<p><p><center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/v1626879891/employee-spotlight-maarten-1_fyzuft.png" /></a></center><p></p>
<h3 id="what-do-you-do-at-datacamp-and-what-does-a-typical-day-look-like-">What do you do at DataCamp and what does a typical day look like?</h3>
<p>I was initially a content developer in the core curriculum team, working on R and Python courses. Then I switched over to curriculum expansion, where I focus on Tableau and Power BI. It’s hard to say what a typical day looks like since it can be quite varied, but there are two ways it generally goes.</p>
<p>One is, I research what it takes to get certified in certain software, and then I put together a rough list to see if it can be made into a viable course. Then it’s a matter of creating conceptual lessons, exercises, and demo videos. The other process is where we work with an external subject matter expert and that person provides the material that should be in a course and how we should present it. Then, we implement that material into Teach, DataCamp’s tool for building courses. Currently, I’m working on two courses simultaneously, but we are improving the process so we can handle more courses at once.</p>
<h3 id="do-you-ever-teach-the-courses-yourself-">Do you ever teach the courses yourself?</h3>
<p>What I really like as a content developer is that we have that opportunity to be the instructors as well. I really like how much of the world you reach, and for me, it was really nice the first time I released a course and got feedback from people outside my network.</p>
<h3 id="where-did-your-interest-in-what-you-do-begin-">Where did your interest in what you do begin?</h3>
<p>I have a background in science, doing a PhD in aquatic ecology, and it was during that time that I came into contact with complex datasets and I was required to do my own data analysis. These were often quite specialized, and back then, R was not where it is today. I remember creating graphs in R was a pain, and I recall our first classes in it were kind of dreadful—no one really understood what we were doing. It was later in my PhD that I understood the value of being able to code your own analyses in your own ways.</p>
<p>One of the main focuses of my PhD was to investigate the effects of land use on water quality and on the presence of mosquitoes in small water bodies. After finishing my PhD, I had the opportunity to participate in a Hackathon that was centered around the spread of dengue fever, a vector-borne disease spread by mosquitoes. It was through this that I got exposed to new technologies and tools in data science, and winning an award during the Hackathon led me to my first job as a data science consultant.</p>
<h3 id="what-brought-you-to-datacamp-">What brought you to DataCamp?</h3>
<p>Since experienced data scientists were in short supply at the time, we were looking to train ourselves. And that is when I found out about DataCamp. I really liked the interactive way of teaching and the practice exercises. As a consultant, I worked on projects involving machine learning, data visualization, and creating dashboards, but my favorite part of my job was when I was giving workshops to clients or students. I thought to myself that there should be a way to do the teaching side of things as a full-time job. Also, I had a Master’s in teaching so I have always been drawn towards education, and when I saw the job opening at DataCamp I saw this as an ideal opportunity to follow that passion.</p>
<h3 id="what-advice-would-you-give-to-anyone-applying-for-a-role-at-datacamp-">What advice would you give to anyone applying for a role at DataCamp?</h3>
<p>I think a lot depends on the department they’re applying to, but in my case, I think it’s great when you know the platform, when you’ve taken some courses, and know how the underlying information is presented. Something new hires will experience is the independence that comes with working on your own projects, although by all means, help is available when needed.
Another feature of working at DataCamp is that there’s always room for improvement. New features are coming out all the time, so don’t be afraid to suggest and try new things. The content team also has varied backgrounds. In addition to myself, we have people from business engineering and economics, marketing analysis, computer science, biostatistics, psychology, geology, and sociology, and this diversity results in interesting ideas for datasets, exercises, and conceptual insights. The short of it is, it does not matter what your background is if you want to get into data science or want to start as a content developer.</p>
<h3 id="outside-of-work-you-founded-an-orchestra-called-conforte-symphonic-https-www-conforte-be-is-that-still-active-">Outside of work you founded an orchestra called <a target="_blank" href="https://www.conforte.be/">“ConForte Symphonic”</a>, is that still active?</h3>
<p>Yes, my wife and I founded it! We’ve always played in orchestras, but there are very few opportunities to play as an amateur. Therefore, we decided to set up our own orchestra late 2019. We played three charity concerts, and were making plans for the future, but then the pandemic happened. Recently, we have the green light to start playing again, and can look forward to future concerts.</p>
<p>Meanwhile, I’ve been looking into ways to use ConForte’s data to make better decisions. For example, I was able to use regression to predict the number of tickets sold for our charity concerts, and we made the right decision to play three concerts instead of our initially planned two—all three of them were sold out.</p>
<h3 id="do-you-find-there-s-a-lot-of-support-in-datacamp-for-projects-like-this-">Do you find there’s a lot of support in DataCamp for projects like this?</h3>
<p>During my onboarding, I was talking to our COO, Martijn, about the founding of our orchestra, and he was really interested to know about that. In general he’s keen to know about peoples’ interests, especially in the case of founding something like a side-project. I also see it as a win-win situation: you learn skills in your spare time that you can apply to your daily job, and vice-versa, so it really keeps you motivated in both areas.</p>
<h3 id="what-do-you-like-doing-in-your-spare-time-">What do you like doing in your spare time?</h3>
<p>I really like the fact that we are playing music again, but other than that most of my time is spent with our two (soon three) kids. As someone with a passion for teaching it’s really been nice to see them wandering about the world and taking it all in for the first time. I really like building up their understanding of things, so if they ask a question I’ll sometimes answer, other times I will ask a question in response so that they think about it—actually it’s a bit like machine learning, you could say, they’re learning by example and repetition, and that’s how machine learning works. By seeing lots of examples, they know how to repeat certain things in certain situations. Anyway, now that they’re off for the summer it’s going to be nice to be spending more time with the family.</p>
<p><em>Would you like to join Maarten at DataCamp? We’re currently hiring in New York; London; Leuven, Belgium; and remote locations. <a target="_blank" href="https://www.datacamp.com/jobs/">Check out our open roles.</a></em></p>


https://www.datacamp.com/community/blog/employee-spotlight-maarten

From mosquitoes to machine learning and music, this week’s Employee Spotlight focuses on Maarten. A former biology researcher and data science consultant, he now works at DataCamp as a content developer.

Employee Spotlight: Maarten

https://www.datacamp.com/community/blog/operationalizing-machine-learning-with-mlops

In this episode of DataFramed, Adel speaks with Alessya Visnjic, CEO and co-founder of WhyLabs, an AI Observability company on a mission to build the interface between AI and human operators. 

Operationalizing Machine Learning with MLOps

<p>Sometimes it’s good to go back to basics, so we put three of our instructors up to the task of role-playing as students getting the Tableau Desktop Specialist certification through Tableau’s official service—using what they learned when creating our <a target="_blank" href="https://www.datacamp.com/tracks/tableau-fundamentals">Tableau skill track</a> and our new course <a target="_blank" href="https://www.datacamp.com/courses/statistical-techniques-in-tableau"><em>Statistical Techniques in Tableau</em></a>. Now that they’ve come out the other side, we decided to interview them to find out about their experiences!</p>
<p><center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/v1626876158/tableau-student-to-certification-1_mhyg40.png" /></a></center><p>


<h3>How did DataCamp help you prepare for the Tableau certification?</h3>
<p>Hadrien: You can be asked to create a visualization or asked which feature to use. DataCamp’s courses give you an overview of what’s available and what you can create with Tableau. They also dive into specific topics, which are the topics the certification is centered around—including analyzing data, creating dashboards, and connecting to data sources.</p>

<p>Sara: DataCamp’s courses cover all the topics that are necessary for the exam. The videos give you an introduction and tell you what is possible using the tool—so, it’s shown in the videos how to connect to a dataset or create a visualization. You can take that knowledge and practice it yourself in the exercises. This is really helpful because during the exam you will be asked to create these visualizations over and over again. So the more you have practiced the quicker you will be at doing these when the time comes. Which is great because it’s timed, and this will free up time for the other questions. Also, exercises are practised in a virtual machine so you get practise with a Windows interface, and this is exactly how you will be working during the exam.</p>


<h3>What surprised you most about the exam?</h3>
<p>Hadrien: Most of the questions don’t require you to build a visualization in Tableau to answer them since they are about where to find certain features—of course, some do require you to build a visualization to gather insights and select the correct answer, but this is in the minority. Also you might get asked about topics that are not in the exam preparation guide, topics which were meant to be reserved for more advanced certification levels, so there won’t be many but it’s good to be aware of that.</p>

<p>Sara: Probably that the exam was multiple choice, as opposed to more active exercises like creating visualizations, and many were related to where you could find certain features. You could also use Google when you weren’t entirely sure, so that was quite a nice surprise.</p>


<h3>What’s the best advice you’d give to someone preparing to take the exam?</h3>

<p>Sara: I’d say two things: on the one hand, practice, practice, practice, make sure you use Tableau a lot, so do things like connecting to datasets and building visualizations until you become comfortable with it. And on the other hand I’d say take a look at some practice exams online to get a feel for what will be asked, and also to identify and shore up any weak points.</p>

<h3>What can we look forward to on the new Tableau course on DataCamp?</h3>

<p>Maarten: You can expect to learn how statistical techniques work, and then see how they are implemented in Tableau. This course is meant for people who have had experience in working with Tableau but want to know more about when and how they should use certain statistical techniques, such as adding a trendline or perform clustering, and also who want to know more about what’s happening behind the scenes.</p>

<h3>What’s your favourite report type that you teach in this course?</h3>

<p>Maarten: I like the predictive reporting this course teaches, so for example you will see our virtual machine predicting the type of dinosaur based on bow length or predict the number of views a YouTube video will get.</p>


<p><center><a target="_blank" href="https://www.datacamp.com/tracks/tableau-fundamentals"><img src="https://res.cloudinary.com/dyd911kmh/image/upload/v1626876551/tableau-student-to-certification-2_gsth2z.png" /></a></center></p>


https://www.datacamp.com/community/blog/tableau-student-to-certification

We talked to three DataCamp instructors who recently took the Tableau Desktop Specialist Certification and asked them about how well our courses prepared them for this.

Tableau: From Student to Certification

<p>You most probably will know by now that data storytelling, accomplished by data visualization, amongst other things, is an essential skill for every data scientist: after you have turned the raw data into understanding, insights and knowledge, you also need to communicate these findings effectively to your audience. </p>
<p>For most beginners, the first Python data visualization library that they use is, naturally, Matplotlib. It is a Python 2D plotting library that enables users to make publication-quality figures. It is quite an extensive library where a <a href="https://www.datacamp.com/community/blog/python-matplotlib-cheat-sheet">cheat sheet</a> will definitely come in handy when you&#39;re learning, but when you manage to use this library effectively, you&#39;ll also be able to get insights and work better with other packages, such as Pandas, that intend to build more plotting integration with Matplotlib as time goes on. </p>
<p>Another package that you&#39;ll be able to tackle easily is Seaborn, the statistical data visualization library of Python. </p>
<p>DataCamp has created a Seaborn cheat sheet for those who are ready to get started with this data visualization library with the help of a handy one-page reference. </p>
<p>You&#39;ll see that this cheat sheet presents you with the five basic steps that you can go through to make beautiful statistical graphs in Python. </p>
<p>Check out the infographic by clicking on the button below:</p>
<p><a href="http://datacamp-community-prod.s3.amazonaws.com/263130e2-2c92-4348-a356-9ed9b5034247"><img alt="Seaborn Python cheat sheet" src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1625839419/Python_Seaborn_Cheat_Sheet_q074wv.png" style="width: 800px; height: 419px;" /></a></p>
<p>This cheat sheet will walk you through the five steps that you need to go through to make these plots: you&#39;ll see how you can load in data, set the figure aesthetics, plot, customize and eventually, show or save your plot with Seaborn.</p>
<p>What might have looked difficult before will definitely be more clear once you start using this cheat sheet! Use it in combination with the <a href="http://seaborn.pydata.org/examples/index.html">Seaborn Gallery</a>, the <a href="http://seaborn.pydata.org/index.html">documentation</a>, and our <a href="https://www.datacamp.com/community/tutorials/seaborn-python-tutorial">Seaborn tutorial</a>.</p>
<p>Also, don&#39;t miss out on our other cheat sheets for data science that cover <a href="https://www.datacamp.com/community/blog/python-scipy-cheat-sheet/">SciPy</a>, <a href="https://www.datacamp.com/community/blog/python-numpy-cheat-sheet/">NumPy</a>, <a href="https://www.datacamp.com/community/blog/scikit-learn-cheat-sheet/">Scikit-Learn</a>, <a href="https://www.datacamp.com/community/blog/bokeh-cheat-sheet-python/">Bokeh</a>, <a href="https://www.datacamp.com/community/blog/python-pandas-cheat-sheet/">Pandas</a> and the <a href="https://www.datacamp.com/community/tutorials/python-data-science-cheat-sheet-basics/">Python basics</a>.</p>


https://www.datacamp.com/community/blog/seaborn-cheat-sheet-python

This Python Seaborn cheat sheet with code samples guides you through the data visualization library that is based on Matplotlib.

This Python Seaborn cheat sheet with code samples guides you through the data visualization library that is based on matplotlib.

Python Seaborn Cheat Sheet

<p>Data visualization and storytelling with your data are essential skills that every data scientist needs to communicate insights gained from analyses effectively to any audience out there.&nbsp;</p>

<p>For most beginners, the first package that they use to get in touch with data visualization and storytelling is, naturally, Matplotlib: it is a Python 2D plotting library that enables users to make publication-quality figures. But, what might be even more convincing is the fact that other packages, such as Pandas, intend&nbsp;to build more plotting integration with Matplotlib as time goes on.</p>

<p>However, what might slow down beginners is the fact that this package is pretty extensive. There is so much that you can do with it and it might be hard to still keep a structure when you&#39;re learning how to work with Matplotlib. &nbsp;&nbsp;</p>

<p>DataCamp has created a Matplotlib cheat sheet for those who might already know how to use the package to their advantage to make beautiful plots in Python, but that still want to keep a one-page reference handy. Of course, for those who don&#39;t know how to work with Matplotlib, this might be the extra push be convinced and to finally get started with data visualization in Python.&nbsp;</p>

<p>(By the way, if you want to get started with this Python package, you might want to consider our <a href="https://www.datacamp.com/community/tutorials/matplotlib-tutorial-python/">Matplotlib tutorial</a>.)</p>

<p>You&#39;ll see that this cheat sheet presents you with the six basic steps that you can go through to make beautiful plots.&nbsp;</p>

<p>Check out the infographic by clicking on the button below:</p>

<p><a href="http://datacamp-community-prod.s3.amazonaws.com/e1a8f39d-71ad-4d13-9a6b-618fe1b8c9e9" target="_blank"><img alt="Python Matplotlib cheat sheet" src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1625838238/Matplotlib_Cheat_Sheet-_Plotting_in_Python_htbtut.png" /></a></p>

<p>With this handy reference, you&#39;ll familiarize yourself in no time with the basics of Matplotlib: you&#39;ll learn how you can prepare your data, create a new plot, use some basic plotting routines to your advantage, add customizations to your plots, and save, show and close the plots that you make.</p>

<p>What might have looked difficult before will definitely be more clear once you start using this cheat sheet! Use it in combination with the <a href="http://matplotlib.org/gallery.html">Matplotlib Gallery</a>, the <a href="http://matplotlib.org/2.0.0/index.html">documentation</a>&nbsp;and our <a href="https://www.datacamp.com/community/tutorials/matplotlib-tutorial-python/">tutorial</a>. &nbsp;&nbsp;</p>

<p>Also, don&#39;t miss out on our other cheat sheets for data science that cover <a href="https://www.datacamp.com/community/blog/python-scipy-cheat-sheet/">SciPy</a>,&nbsp;<a href="https://www.datacamp.com/community/blog/python-numpy-cheat-sheet/">Numpy</a>,&nbsp;<a href="https://www.datacamp.com/community/blog/scikit-learn-cheat-sheet/">Scikit-Learn</a>,&nbsp;<a href="https://www.datacamp.com/community/blog/bokeh-cheat-sheet-python/">Bokeh</a>,&nbsp;<a href="https://www.datacamp.com/community/blog/python-pandas-cheat-sheet/">Pandas</a>&nbsp;and the&nbsp;<a href="https://www.datacamp.com/community/tutorials/python-data-science-cheat-sheet-basics/">Python basics</a>.</p>


https://www.datacamp.com/community/blog/python-matplotlib-cheat-sheet

This Matplotlib cheat sheet introduces you to the basics that you need to plot your data with Python and includes code samples. 

This CHEAT SHEET introduces you to the basics of MATPLOTLIB that are needed to plot your data with PYTHON. It also includes code samples. 

(Cheat Sheet) Matplotlib: Plotting in Python

Matplotlib Cheat Sheet: Plotting in Python

<p>The tidyverse is a powerful collection of R packages that you can use for data science. They are designed to help you to transform and visualize data. All packages within this collection share an underlying philosophy and common APIs. </p>
<p>As you might know, DataCamp recently launched the <a href="https://www.datacamp.com/courses/introduction-to-the-tidyverse">Introduction to the Tidyverse</a> course together with David Robinson, Data Scientist at Stack Overflow.</p>
<p>Now, DataCamp has created a tidyverse cheat sheet for beginners that have already taken the course and that still want a handy one-page reference or for those who need an extra push to get started on discovering this popular collection of packages. You must have already run into packages such as <code>ggplot2</code> and <code>dplyr</code>, so this cheat sheet will definitely come in handy!</p>
<p>It&#39;s a quick guide through the basics of manipulating and visualizing your data the powerful tools that the tidyverse has to offer in R! </p>
<p><a href="http://datacamp-community-prod.s3.amazonaws.com/c1fae72f-d2d7-4646-9dce-dd0f8fb5c5e8"><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1625839345/Tidyverse_Cheat_Sheet_For_Beginners_d4lkxp.png"/></a></p>
<p>The tidyverse cheat sheet will guide you through some general information on the tidyverse, and then covers topics such as useful functions, loading in your data, manipulating it with <code>dplyr</code> and lastly, visualize it with <code>ggplot2</code>. </p>
<p>In short, everything that you need to kickstart your data science learning with R!</p>
<p>Do you want to learn more? Also check out and star the <a href="https://www.datacamp.com/courses/exploratory-data-analysis-in-r-case-study">Exploratory Data Analysis in R: Case Study</a> course, also taught by David Robinson, for free now! </p>
<p>Also, don&#39;t miss out on our <a href="https://www.datacamp.com/community/tutorials/data-table-cheat-sheet">data.table cheat sheet</a> for data manipulation in R and our <a href="https://www.datacamp.com/community/data-science-cheatsheets">other cheat sheets for data science</a>.</p>
<p><strong>(Click above to download a printable version or read the online version below)</strong>. </p>


https://www.datacamp.com/community/blog/tidyverse-cheat-sheet-beginners

This tidyverse cheat sheet will guide you through the basics of the tidyverse, and 2 of its core packages: dplyr and ggplot2! 

Tidyverse Cheat Sheet For Beginners

<p>By now, you will have already learned that NumPy, one of the fundamental packages for scientific computing, forms at least for a part&nbsp;the fundament of other important&nbsp;packages that you might use used for data manipulation and machine learning with Python. One of those packages is SciPy, another one&nbsp;of the core packages for scientific computing in Python that provides mathematical algorithms and convenience functions built on the&nbsp;NumPy extension of Python.&nbsp;</p>

<p>You might now wonder why this library might come in handy for data science.&nbsp;</p>

<p>Well, SciPy has many modules that will help you to understand some of the basic components that you need to master when you&#39;re learning data science, namely, math, stats and machine learning. You can find out what other things you need to tackle to learn data science <a href="https://www.datacamp.com/community/tutorials/learn-data-science-infographic/">here</a>. You&#39;ll see that for statistics, for example, a module like&nbsp;<code>scipy.stats</code>, etc. will definitely be of interest to you.</p>

<p>The other topic that was mentioned was machine learning: here, the&nbsp;<code>scipy.linalg</code>&nbsp;and <code>scipy.sparse</code> modules will offer everything that you&#39;re looking for to understand machine learning concepts such as eigenvalues, regression, and matrix multiplication...</p>

<p>But, what is maybe the most obvious is that most machine learning techniques deal with high-dimensional data and that data is often represented as matrices. What&#39;s more, you&#39;ll need to understand how to manipulate these matrices. &nbsp;</p>

<p>That is why DataCamp has made a SciPy cheat sheet that will help you to master linear algebra with Python.&nbsp;</p>

<p>Take a look by clicking on the button below:</p>

<p><a href="http://datacamp-community-prod.s3.amazonaws.com/dfdb6d58-e044-4b38-bab3-5de0b825909b"><img alt="python scipy cheat sheet" src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1625838166/SciPy_Cheat_Sheet-_Linear_Algebra_in_Python_ff0oa8.png" style="width: 800px; height: 551px;" /></a></p>

<p>&nbsp;</p>

<p>You&#39;ll see that this SciPy cheat sheet covers the basics of linear algebra&nbsp;that you need to get started: it provides a brief explanation of what the&nbsp;library has to offer and how you can use it to interact with NumPy, and goes on to summarize topics in linear algebra, such as matrix creation, matrix functions,&nbsp;basic routines that you can perform with matrices, and matrix decompositions from <code>scipy.linalg</code>. Sparse matrices are also included, with their own routines, functions, and decompositions from the <code>scipy.sparse</code> module.&nbsp;</p>
<p><strong>(Above is the printable version of this cheat sheet)</strong></p>

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<h2>Python for Data-Science <em>Cheat Sheet</em>&#58; SciPy - Linear Algebra</h2>
<h2>SciPy</h2>
<p>The SciPy library is one of the core packages for scientific computing that provides mathematical algorithms and convenience functions built on the NumPy extension of Python.</p>
<h2>Asking For Help</h2>
<tr><td><code>&#62;&#62;&#62; help&#40;scipy.linalg.diagsvd&#41;</code></td></tr>
<h2>Interacting With NumPy</h2>
<table>
<tr><td><code>&#62;&#62;&#62; import numpy as np </code></td></tr>
<tr><td><code>&#62;&#62;&#62; a &#58; np.array&#40;&#91;1&#44;2&#44;3&#93;&#41;</code></td></tr>
<tr><td><code>&#62;&#62;&#62; b &#58; np.array&#40;&#91;&#40;1+5j&#44;2j&#44;3j&#41;&#44; &#40;4j&#44;5j&#44;6j&#41;&#93;&#41;</code></td></tr>
<tr><td><code>&#62;&#62;&#62; c &#58; np.array&#40;&#91;&#91;&#40;1.5&#44;2&#44;3&#41;&#44; &#40;4&#44;5&#44;6&#41;&#93;&#44; &#91;&#40;3&#44;2&#44;1&#41;&#44; &#40;4&#44;5&#44;6&#41;&#93;&#93;&#41;</code></td></tr>
</table>
<h3>Index Tricks</h3>
<table>
<tr><td><code>&#62;&#62;&#62; np.mgrid&#91;0&#58;5&#44;0&#58;5&#93;</code></td><td> Create a dense meshgrid</td></tr>
<tr><td><code>&#62;&#62;&#62; np.ogrid&#91;0&#58;2&#44;0&#58;2&#93; </code></td></tr>
<tr><td><code>&#62;&#62;&#62; np.r_&#91;3&#44;&#91;0&#93;*5&#44;-1&#58;1&#58;10j&#93;</code></td><td>Stack arrays vertically &#40;row-wise&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; np.c_&#91;b&#44;c&#93;</code></td></tr>
</table>
<h3>Shape Manipulation</h3>
<table>
<tr><td><code>&#62;&#62;&#62; np.transpose&#40;b&#41;</code></td><td> Permute array dimensions</td></tr>
<tr><td><code>&#62;&#62;&#62; b.flatten&#40;&#41;</code></td><td>Flatten the array</td></tr>
<tr><td><code>&#62;&#62;&#62; np.hstack&#40;&#40;b&#44;c&#41;&#41;</code></td><td>Stack arrays horizontally &#40;column-wise&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; np.vstack&#40;&#40;a&#44;b&#41;&#41;</code></td><td>Stack arrays vertically &#40;row-wise&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; np.hsplit&#40;c&#44;2&#41;</code></td><td>Split the array horizontally at the 2nd index</td></tr>
<tr><td><code>&#62;&#62;&#62; np.vpslit&#40;d&#44;2&#41;</code></td></tr>
</table>
<h3>Polynomials </h3>
<table>
<tr><td><code>&#62;&#62;&#62; from numpy import poly1d</code></td></tr>
<tr><td><code>&#62;&#62;&#62; p &#58; poly1d&#40;&#91;3&#44;4&#44;5&#93;&#41;</code></td><td>Create a polynomial object</td></tr>
</table>
<h3>Vectorizing Functions</h3>
<table>
	<table>
	<tr><td><code>&#62;&#62;&#62; def myfunc&#40;a&#41;&#58;</code></td></tr>
	<tr><td><code>&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;if a &#8249; 0&#58; </code></td></tr>
	<tr><td><code>&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;return a*2</code></td></tr>
	<tr><td><code>&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;else&#58;</code></td></tr>
	<tr><td><code>&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;return a/2</code></td></tr>
	<tr><td><code>&#62;&#62;&#62; np.vectorize&#40;myfunc&#41;</code></td><td> Vectorize functions</td></tr>
</table>
<h3>Type Handling </h3>
<table>
<tr><td><code>&#62;&#62;&#62; np.real&#40;b&#41;</code></td><td>Return the real part of the array elements </td></tr>
<tr><td><code>&#62;&#62;&#62; np.imag&#40;b&#41;</code></td><td>Return the imaginary part of the array elements</td></tr>
<tr><td><code>&#62;&#62;&#62; np.real_if_close&#40;c&#44;tol&#58;1000&#41; </code></td><td>Return a real array if complex parts close to 0</td></tr>
<tr><td><code>&#62;&#62;&#62; np.cast&#91;'f'&#93;&#40;np.pi&#41;</code></td><td>Cast object to a data type</td></tr>
</table>
<h3>Other Useful Functions</h3>
<table>
<tr><td><code>&#62;&#62;&#62; np.angle&#40;b&#44;deg&#58;True&#41;</code></td><td>Return the angle of the complex argument</td></tr>
<tr><td><code>&#62;&#62;&#62; g &#58; np.linspace&#40;0&#44;np.pi&#44;num&#58;5&#41;</code></td><td>Create an array of evenly spaced values &#40;number of samples&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; g &#91;3&#58;&#93; +&#58; np.pi</code></td></tr>
<tr><td><code>&#62;&#62;&#62; np.unwrap&#40;g&#41; </code></td></tr>
<tr><td><code>&#62;&#62;&#62; np.logspace&#40;0&#44;10&#44;3&#41;</code></td><td>Create an array of evenly spaced values &#40;log scale&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; np.select&#40;&#91;c&#60;4&#93;&#44;&#91;c*2&#93;&#41;</code></td><td>Return values from a list of arrays depending on conditions</td></tr>
<tr><td><code>&#62;&#62;&#62; misc.factorial&#40;a&#41;</code></td><td>Factorial </td></tr>
<tr><td><code>&#62;&#62;&#62; misc.comb&#40;10&#44;3&#44;exact&#58;True&#41;</code></td><td>Combine N things taken at k time</td></tr>
<tr><td><code>&#62;&#62;&#62; misc.central_diff_weights&#40;3&#41;</code></td><td>Weights for Np-point central derivative</td></tr>
<tr><td><code>&#62;&#62;&#62; misc.derivative&#40;myfunc&#44;1.0&#41;</code></td><td>Find the n-th derivative of a function at a point</td></tr>
</table>

<h3>﻿Linear Algebra</h3>
<p>You&#39;ll use the linalg and sparse modules. Note thatscipy.linalg contains and expands onnumpy.linalg. </p>
<table>
<tr><td><code>&#62;&#62;&#62; from scipy import linalg&#44; sparse</code></td></tr>
</table>
<h3>Creating Matrices</h3>
<table>
<tr><td><code>&#62;&#62;&#62; A &#58; np.matrix&#40;np.random.random&#40;&#40;2&#44;2&#41;&#41;&#41;</code></td></tr>
<tr><td><code>&#62;&#62;&#62; B &#58; np.asmatrix&#40;b&#41;</code></td></tr>
<tr><td><code>&#62;&#62;&#62; C &#58; np.mat&#40;np.random.random&#40;&#40;10&#44;5&#41;&#41;&#41;</code></td></tr>
<tr><td><code>&#62;&#62;&#62; D &#58; np.mat&#40;&#91;&#91;3&#44;4&#93;&#44; &#91;5&#44;6&#93;&#93;&#41;</code></td></tr>
</table>



<table>
</table>
<h3>Basic Matrix Routines</h3>
<table>
</table>
<h4>Inverse</h4>
<table>
<tr><td><code>&#62;&#62;&#62; A.I</code></td><td>Inverse</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.inv&#40;A&#41;</code></td><td>Inverse</td></tr>
</table>
<h4>Transposition</h4>
<table>
<tr><td><code>&#62;&#62;&#62; A.T</code></td><td>Tranpose matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; A.H</code></td><td>Conjugate transposition</td></tr>
</table>
<h4>Trace</h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.trace&#40;A&#41;</code></td><td>Trace</td></tr>
</table>
<h4>Norm</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.norm&#40;A&#41;</code></td><td> Frobenius norm</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.norm&#40;A&#44;1&#41;</code></td><td> L1 norm &#40;max column sum&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.norm&#40;A&#44;np.inf&#41;</code></td><td> L inf norm &#40;max row sum&#41;</td></tr>
</table>
<h4>Rank</h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.linalg.matrix_rank&#40;C&#41;</code></td><td> Matrix rank</td></tr>
</table>
<h4>Determinant</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.det&#40;A&#41;</code></td><td>Determinant</td></tr>
</table>
<h4>Solving linear problems</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.solve&#40;A&#44;b&#41;</code></td><td>Solver for dense matrices</td></tr>
<tr><td><code>&#62;&#62;&#62; E &#58; np.mat&#40;a&#41;.T</code></td><td>Solver for dense matrices</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.lstsq&#40;F&#44;E&#41;</code></td><td>Least-squares solution to linear matrix equation</td></tr>
</table>
<h4> Generalized inverse</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.pinv&#40;C&#41;</code></td><td> Compute the pseudo-inverse of a matrix &#40;least-squares solver</td></tr>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.pinv2&#40;C&#41;</code></td><td>Compute the pseudo-inverse of a matrix &#40;SVD&#41;</td></tr>
</table>

<h3>Creating Sparse Matrices</h3>
<table>
<tr><td><code>&#62;&#62;&#62; F &#58; np.eye&#40;3&#44; k&#58;1&#41;</code></td><td> Create a 2X2 identity matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; G &#58; np.mat&#40;np.identity&#40;2&#41;&#41; </code></td><td>Create a 2x2 identity matrix </td></tr>
<tr><td><code>&#62;&#62;&#62; C&#91;C &#62; 0.5&#93; &#58; 0 </code></td></tr>
<tr><td><code>&#62;&#62;&#62; H &#58; sparse.csr_matrix&#40;C&#41; </code></td><td>Compressed Sparse Row matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; I &#58; sparse.csc_matrix&#40;D&#41; </code></td><td>Compressed Sparse Column matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; J &#58; sparse.dok_matrix&#40;A&#41; </code></td><td>Dictionary Of Keys matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; E.todense&#40;&#41;</code></td><td>Sparse matrix to full matrix</td></tr>
<tr><td><code>&#62;&#62;&#62; sparse.isspmatrix_csc&#40;A&#41; </code></td><td>Identify sparse matrix</td></tr>
</table>
<h3>Sparse Matrix Routines</h3>
<table>
</table>
<h4>Inverse</h4>
<table>
<tr><td><code>&#62;&#62;&#62; sparse.linalg.inv&#40;I&#41;</code></td><td>Inverse</td></tr>
</table>
<h4>Norm </h4>
<table>
<tr><td><code>&#62;&#62;&#62; sparse.linalg.norm&#40;I&#41; </code></td><td>Norm</td></tr>
</table>
<h4> Solving linear problems </h4>
<table>
<tr><td><code>&#62;&#62;&#62; sparse.linalg.spsolve&#40;H&#44;I&#41;</code></td><td>Solver for sparse matrices</td></tr>
</table>
<h3>Sparse Matrix Functions</h3>
<table>
<tr><td><code>&#62;&#62;&#62; la&#44; v &#58; sparse.linalg.eigs&#40;F&#44;1&#41;</code></td><td>Eigenvalues and eigenvectors</td></tr>
<tr><td><code>&#62;&#62;&#62; sparse.linalg.svds&#40;H&#44; 2&#41;</code></td><td> SVD</td></tr>
<tr><td><code>&#62;&#62;&#62; sparse.linalg.expm&#40;I&#41; </code></td><td>Sparse matrix exponential</td></tr>
</table>

<h3>Matrix Functions</h3>
<h4>Addition</h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.add&#40;A&#44;D&#41;</code></td><td>Addition</td></tr>
</table>
<h4> Subtraction</h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.subtract&#40;A&#44;D&#41;</code></td><td> Subtraction</td></tr>
</table>
<h4> Division</h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.divide&#40;A&#44;D&#41;</code></td><td> Division</td></tr>
</table>
<h4> Multiplication</h4>
<table>
<tr><td><code>&#62;&#62;&#62; A @ D</code></td><td>Multiplication operator &#40;Python 3&#41;</td></tr>

<tr><td><code>&#62;&#62;&#62; np.multiply&#40;D&#44;A&#41;</code></td><td> Multiplication</td></tr>
<tr><td><code>&#62;&#62;&#62; np.dot&#40;A&#44;D&#41;</code></td><td>Dot product</td></tr>
<tr><td><code>&#62;&#62;&#62; np.vdot&#40;A&#44;D&#41;</code></td><td> Vector dot product</td></tr>
<tr><td><code>&#62;&#62;&#62; np.inner&#40;A&#44;D&#41;</code></td><td>Inner product</td></tr>
<tr><td><code>&#62;&#62;&#62; np.outer&#40;A&#44;D&#41;</code></td><td>Outer product</td></tr>
<tr><td><code>&#62;&#62;&#62; np.tensordot&#40;A&#44;D&#41;</code></td><td>Tensor dot product</td></tr>
<tr><td><code>&#62;&#62;&#62; np.kron&#40;A&#44;D&#41;</code></td><td> Kronecker product</td></tr>
</table>
<h4>Exponential Functions</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.expm&#40;A&#41;</code></td><td> Matrix exponential</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.expm2&#40;A&#41;</code></td><td>Matrix exponential &#40;Taylor Series&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.expm3&#40;D&#41;</code></td><td>Matrix exponential &#40;eigenvalue decomposition&#41;</td></tr>
</table>
<h4>Logarithm Function</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.logm&#40;A&#41;</code></td><td> Matrix logarithm </td></tr>
</table>
<h4>Trigonometric Functions</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.sinm&#40;D&#41;</code></td><td> Matrix sine</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.cosm&#40;D&#41;</code></td><td> Matrix cosine</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.tanm&#40;A&#41;</code></td><td> Matrix tangent</td></tr>
</table>
<h4>Hyperbolic Trigonometric Functions</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.sinhm&#40;D&#41;</code></td><td>Hypberbolic matrix sine</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.coshm&#40;D&#41;</code></td><td>Hyperbolic matrix cosine</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.tanhm&#40;A&#41;</code></td><td>Hyperbolic matrix tangent</td></tr>
</table>
<h4>Matrix Sign Function </h4>
<table>
<tr><td><code>&#62;&#62;&#62; np.signm&#40;A&#41;</code></td><td>Matrix sign function</td></tr>
</table>
<h4>Matrix Square Root</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.sqrtm&#40;A&#41;</code></td><td>Matrix square root</td></tr>
</table>
<h4>Arbitrary Functions</h4>
<table>
<tr><td><code>&#62;&#62;&#62; linalg.funm&#40;A&#44; lambda x&#58; x*x&#41;</code></td><td>Evaluate matrix function</td></tr>
</table>

<h3>Decompositions</h3>
<table>
</table>
<h4>Eigenvalues and Eigenvectors</h4>
<table>
<tr><td><code>&#62;&#62;&#62; la&#44; v &#58; linalg.eig&#40;A&#41; </code></td><td>Solve ordinary or generalized eigenvalue problem for square matrix </td></tr>
<tr><td><code>&#62;&#62;&#62; l1&#44; l2 &#58; la</code></td><td> Unpack eigenvalues</td></tr>
<tr><td><code>&#62;&#62;&#62; v&#91;&#58;&#44;0&#93;</code></td><td>First eigenvector</td></tr>
<tr><td><code>&#62;&#62;&#62; v&#91;&#58;&#44;1&#93;</code></td><td>Second eigenvector</td></tr>
<tr><td><code>&#62;&#62;&#62; linalg.eigvals&#40;A&#41;</code></td><td> Unpack eigenvalues</td></tr>
</table>
<h4>Singular Value Decomposition </h4>
<table>
<tr><td><code>&#62;&#62;&#62; U&#44;s&#44;Vh &#58; linalg.svd&#40;B&#41;</code></td><td>Singular Value Decomposition &#40;SVD&#41;</td></tr>
<tr><td><code>&#62;&#62;&#62; M&#44;N &#58; B.shape </code></td></tr>
<tr><td><code>&#62;&#62;&#62; Sig &#58; linalg.diagsvd&#40;s&#44;M&#44;N&#41;</code></td><td>Construct sigma matrix in SVD</td></tr>
<h3>LU Decomposition</h3>
<table><tr><td><code>&#62;&#62;&#62; P&#44;L&#44;U &#58; linalg.lu&#40;C&#41;</code></td><td>LU Decomposition</td></tr></table>


<h3>Sparse Matrix Decompositions</h3>
<tr><td><code>&#62;&#62;&#62; np.info&#40;np.matrix&#41;</code></td></tr>
<br>
<br>
<br>
<br>
<p>PS.&nbsp;Don&#39;t miss our other Python cheat sheets for data science that cover <a href="https://www.datacamp.com/community/blog/python-numpy-cheat-sheet/">Numpy</a>&#44;&nbsp;<a href="https://www.datacamp.com/community/blog/scikit-learn-cheat-sheet/">Scikit-Learn</a>&#44;&nbsp;<a href="https://www.datacamp.com/community/blog/bokeh-cheat-sheet-python/">Bokeh</a>,&nbsp;<a href="https://www.datacamp.com/community/blog/python-pandas-cheat-sheet/">Pandas</a>&nbsp;and the&nbsp;<a href="https://www.datacamp.com/community/tutorials/python-data-science-cheat-sheet-basics/">Python basics</a>.</p>

</div>


https://www.datacamp.com/community/blog/python-scipy-cheat-sheet

This Python cheat sheet is a handy reference with code samples for doing linear algebra with SciPy and interacting with NumPy.

SciPy Cheat Sheet: Linear Algebra in Python 

<section>
<p>Even though the <code>data.frame</code> object is one of the core objects to hold data in R, you&#39;ll find that it&#39;s not really efficient when you&#39;re working with time series data. You&#39;ll find yourself wanting a more flexible time series class in R that offers a variety of methods to manipulate your data.</p>

<p>&nbsp;<code>xts</code> &nbsp;or the Extensible Time Series&nbsp;is one of such packages that offers such a time series object. It&#39;s a powerful R package&nbsp;that&nbsp;provides an extensible time series class, enabling uniform handling of many R time series classes by extending <code>zoo</code>, which is the package that is the creator for an S3 class of indexed totally ordered observations which includes irregular time series.</p>

<p><code><tt>xts</tt></code> has a lot to offer to make your time series analysis fast and mistake free, but it can take some time to get used to it.&nbsp;</p>

<p>This <code>xts</code> cheat sheet provides you not only with an overview of the <code>xts</code> object, how to create and inspect them, but also goes deeper into how you can manipulate time series with <code>xts</code>: you&#39;ll see how to replace and update values, how to select, index and subset your objects, how to handle missing values and how to perform arithmetic operations.</p>

<p>Click on the button below to see (and download) the xts cheat sheet:&nbsp;</p>

<p><a href="http://datacamp-community-prod.s3.amazonaws.com/72771032-0653-4d87-a798-4a83879e99c8" target="_blank"><img alt="" src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1625838439/xts_Cheat_Sheet-_Time_Series_in_R_nbiik0.png" style="width: 800px; height: 551px;" /></a></p>

<p><strong>(Click above to download a printable version or read the online version below.)&nbsp;</strong></p>

<p>This cheat sheet will help you to get yourself up to speed in no time!&nbsp;</p>

<div id="scoped-content">
<style type="text/css">:target:before { content:""; display:block; height:150px; margin:-150px 0 0; } h3 {font-weight:normal; } h4 { 	font-weight: lighter; }
</style>
<h2>R For Data Science Cheat Sheet: xts</h2>

<p>eXtensible Time Series (xts) is a powerful package that provides an extensible time series class, enabling uniform handling of many R time series classes by extending zoo.</p>

<p>Load the package as follows:</p>

<pre>
<code>library(xts)</code></pre>

<h3>Xts Objects</h3>

<p>xts objects have three main components:</p>

<ul>
	<li>coredata: always a matrix for xts objects</li>
	<li>index: vector of any <code>Date</code>, <code>POSIXct</code>, <code>chron</code>, <code>yearmon</code>, <code>yearqtr</code>, or <code>DateTime</code> classes</li>
	<li>xtsAttributes: arbitrary attributes</li>
</ul>

<h2>Creating xts Objects</h2>

<pre>
<code>xts1 &lt;- xts(x=1:10, order.by=Sys.Date()-1:10)
data &lt;- rnorm(5)
dates &lt;- seq(as.Date("2017-05-01"), length=5, by="days")
xts2 &lt;- xts(x=data, order.by=dates)
xts3 &lt;- xts(x=rnorm(10), order.by=as.POSIXct(Sys.Date()+1:10), born=as.POSIXct("1899-05-08")
xts4 &lt;- xts(x=1:10, order.by=Sys.Date()+1:10)</code></pre>

<h3>Convert To And From xts</h3>

<pre>
<code>data(AirPassengers)
xts5 &lt;- as.xts(AirPassengers)</code></pre>

<h3>Import From Files</h3>

<pre>
<code>dat &lt;- read.csv(tmp_file)
xts(dat, order.by=as.Date(rownames(dat),"%m/%d/%Y"))
dat_zoo &lt;- read.zoo(tmp_file, index.column=0, sep=",", format="%m/%d/%Y")
dat_zoo &lt;- read.zoo(tmp,sep=",",FUN=as.yearmon)
dat_xts &lt;- as.xts(dat_zoo)</code></pre>

<h2>Inspect Your Data</h2>

<p>Extract core data of objects</p>

<pre>
<code>core_data &lt;- coredata(xts2)</code></pre>

<p>Extract index from objects</p>

<pre>
<code>index(xts1)</code></pre>

<h3>Class Attributes</h3>

<p>Get index class</p>

<pre>
<code>indexClass(xts2)</code></pre>

<p>Replacing index class</p>

<pre>
<code>indexClass(convertIndex(xts,'POSIXct'))</code></pre>

<p>Get index class</p>

<pre>
<code>indexTZ(xts5)</code></pre>

<p>Change format of time display</p>

<pre>
<code>indexFormat(xts5) &lt;- "%Y-%m-%d"</code></pre>

<h3>Time Zones</h3>

<p>Change the time zone</p>

<pre>
<code>tzone(xts1) &lt;- "Asia/Hong_Kong"</code></pre>

<p>Extract the current time zone</p>

<pre>
<code>tzone(xts1)</code></pre>

<h3>Periods, Periodicity &amp; Timestamps</h3>

<p>Estimate frequency of observations</p>

<pre>
<code>periodicity(xts5)</code></pre>

<p>Convert xts5 to yearly OHLC</p>

<pre>
<code>to.yearly(xts5)</code></pre>

<p>Convert <code>xts3</code> to monthly OHLC</p>

<pre>
<code>to.monthly(xts3)</code></pre>

<p>Convert <code>xts5</code> to quarterly OHLC</p>

<pre>
<code>to.quarterly(xts5)</code></pre>

<p>Convert to quarterly OHLC</p>

<pre>
<code>to.period(xts5,period="quarters")</code></pre>

<p>Convert to yearly OHLC</p>

<pre>
<code>to.period(xts5,period="years")</code></pre>

<p>Count the months in <code>xts5</code></p>

<pre>
<code>nmonths(xts5)</code></pre>

<p>Count the quarters in <code>xts5</code></p>

<pre>
<code>nquarters(xts5)</code></pre>

<p>Count the years in <code>xts5</code></p>

<pre>
<code>nyears(xts5)</code></pre>

<p>Make index unique</p>

<pre>
<code>make.index.unique(xts3,eps=1e-4)</code></pre>

<p>Remove duplicate times</p>

<pre>
<code>make.index.unique(xts3,drop=TRUE)</code></pre>

<p>Round index time to the next <code>n</code> seconds</p>

<pre>
<code>align.time(xts3, n=3600)</code></pre>

<h3>Other Useful Functions</h3>

<p>Extract raw numeric index of <code><tt>xts1</tt></code></p>

<pre>
<code>.index(xts4)</code></pre>

<p>value of weekday&nbsp;in index of <code>xts3</code></p>

<pre>
<code>.indexwday(xts3)</code></pre>

<p>Value of hour in index of <code>xts3</code></p>

<pre>
<code>.indexhour(xts3)</code></pre>

<p>Extract first observation of <code>xts3</code>&nbsp;</p>

<pre>
<code>start(xts3)</code></pre>

<p>Extract last observation of <code>xts4</code>&nbsp;</p>

<pre>
<code>end(xts4)</code></pre>

<p>Display structure of <code>xts3</code>&nbsp;</p>

<pre>
<code>str(xts3) </code></pre>

<p>Extract raw numeric index of <code>xts1</code></p>

<pre>
<code>time(xts1)</code></pre>

<p>First part of <code>xts2</code></p>

<pre>
<code>head(xts2)</code></pre>

<p>Last part of <code>xts2</code>&nbsp;</p>

<pre>
<code>tail(xts2)</code></pre>

<p>&nbsp;</p>

<h2>Export <code>xts</code> Objects</h2>

<pre>
<code>data_xts &lt;- as.xts(matrix)
tmp &lt;- tempfile()
write.zoo(data_xts,sep=",",file=tmp)</code></pre>

<h2>Replace &amp; Update</h2>

<p>Replace values in <code>xts2</code> on dates with <code><tt>0</tt></code>&nbsp;</p>

<pre>
<code>xts2[dates] &lt;- 0 </code></pre>

<p>Replace dates from 1961 with <code>NA</code>&nbsp;</p>

<pre>
<code>xts5["1961"] &lt;- NA</code></pre>

<p>Replace the value at 1 specific index with <code>NA</code></p>

<pre>
<code>xts2["2016-05-02"] &lt;- NA </code></pre>

<p>&nbsp;&nbsp;</p>

<h2>Applying Functions</h2>

<p>Locate endpoints by time&nbsp;</p>

<pre>
<code>ep1 &lt;- endpoints(xts4,on="weeks",k=2)  
ep2 &lt;- endpoints(xts5,on="years") </code></pre>

<p>Calculate the yearly mean&nbsp;</p>

<pre>
<code>period.apply(xts5,INDEX=ep2,FUN=mean)</code></pre>

<p>Split <code>xts5</code> by year</p>

<pre>
<code>xts5_yearly &lt;- split(xts5,f="years")</code></pre>

<p>Create a list of yearly means&nbsp; &nbsp;</p>

<pre>
<code>lapply(xts5_yearly,FUN=mean) </code></pre>

<p>Find the last observation in each year in <code>xts5</code></p>

<pre>
<code>do.call(rbind,  lapply(split(xts5,"years"), function(w) last(w,n="1 month"))) </code></pre>

<p>Calculate cumulative annual passengers</p>

<pre>
<code>do.call(rbind,  lapply(split(xts5,"years"),  cumsum)) </code></pre>

<p>Apply standard deviation&nbsp;to rolling margins of <code>xts5</code></p>

<pre>
<code>rollapply(xts5, 3, sd)  </code></pre>

<h2>Selecting, Subsetting &amp; Indexing</h2>

<h3>Select</h3>

<pre>
<code>mar55 &lt;- xts5["1955-03"] #Get value for March 1955</code></pre>

<h3>Subset</h3>

<p>Get all data from 1954&nbsp;</p>

<pre>
<code>xts5_1954 &lt;- xts5["1954"] </code></pre>

<p>Extract data from Jan to March &lsquo;54&nbsp;</p>

<pre>
<code>xts5_janmarch &lt;- xts5["1954/1954-03"]</code></pre>

<p>Get all data until March &lsquo;54&nbsp;&nbsp;</p>

<pre>
<code>xts5_janmarch &lt;- xts5["/1954-03"] </code></pre>

<p>Subset <code>xts4</code> using <code>ep2</code>&nbsp;</p>

<pre>
<code>xts4[ep1] </code></pre>

<h3><code>first()</code> and <code>last()</code></h3>

<pre>
<code>first(xts4,'1 week') #Extract first 1 week
first(last(xts4,'1 week'),'3 days') #Get first 3 days of the last week of data</code></pre>

<h3>Indexing</h3>

<p>Extract rows with the index of <code>xts3</code>&nbsp;</p>

<pre>
<code>xts2[index(xts3)] </code></pre>

<p>Extract rows using the vector <code>days</code>&nbsp;</p>

<pre>
<code>days &lt;- c("2017-05-03","2017-05-23") 
xts3[days] </code></pre>

<p>Extract rows using <code>days</code> as <code>POSIXct</code>&nbsp;</p>

<pre>
<code>xts2[as.POSIXct(days,tz="UTC")] </code></pre>

<p>Index of weekend days</p>

<pre>
<code>index&lt;-which(.indexwday(xts1)==0|.indexwday(xts1)==6) </code></pre>

<p>Extract weekend days of <code>xts1</code>&nbsp;</p>

<pre>
<code>xts1[index] </code></pre>

<h2>Missing Values</h2>

<p>Omit NA values in <code>xts5</code>&nbsp;</p>

<pre>
<code>na.omit(xts5) </code></pre>

<p>Fill missing values in <code>xts2</code>&nbsp;using last observation</p>

<pre>
<code>xts_last &lt;- na.locf(xts2) </code></pre>

<p>Fill missing values in <code>xts2</code> using next observation</p>

<pre>
<code>xts_last &lt;- na.locf(xts2,  fromLast=TRUE)</code></pre>

<p>Interpolate <code>NA</code>s</p>

<pre>
<code>na.approx(xts2)  </code></pre>

<h2>Arithmetic Operations</h2>

<h3><code>coredata()</code> or <code>as.numeric()</code></h3>

<pre>
<code>xts3 + as.numeric(xts2) #Addition
xts3 * as.numeric(xts4) #Multiplication
coredata(xts4) - xts3 #Subtraction
coredata(xts4) / xts3 #Division</code></pre>

<h3>Shifting Index Values</h3>

<p>Period-over-period differences&nbsp;</p>

<pre>
<code>xts5 - lag(xts5) </code></pre>

<p>Lagged differences</p>

<pre>
<code>diff(xts5,lag=12,differences=1) </code></pre>

<h3>Reindexing</h3>

<pre>
<code>xts1 + merge(xts2,index(xts1),fill=0) #Addition
xts1 - merge(xts2,index(xts1),fill=na.locf) #Subtraction</code></pre>

<h2>Merging</h2>

<pre>
<code>merge(xts2,xts1,join='inner') # Inner join of xts2 and xts1
merge(xts2,xts1,join='left',fill=0) #Left join of xts2 and xts1,
rbind(xts1, xts4)</code></pre>

<h2>Going Further</h2>

<p>Want to know more about <code>xts</code>? Check out DataCamp&#39;s <a href="https://www.datacamp.com/courses/manipulating-time-series-data-in-r-with-xts-zoo">Manipulating Time Series Data in R with </a><a href="https://www.datacamp.com/courses/manipulating-time-series-data-in-r-with-xts-zoo">xts</a><a href="https://www.datacamp.com/courses/manipulating-time-series-data-in-r-with-xts-zoo">&nbsp;&amp; zoo</a>&nbsp;course!&nbsp;</p>
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