## Converting a distribution to Z-scale

In this exercise, you will convert the ratings for the Australian red wine to the Z-scale. The data are already loaded into your workspace as `ratings_australia`

.

R provides you with an easy way to do this. Given a list of observations, you can transform these observations to Z-scores using the `scale()`

function.

### Instructions

- Convert the ratings stored in
`ratings_australia`

to Z-scores and assign the result to`z_scores_australia`

. - Plot the histograms for the original ratings and the Z-scores next to each other. The command
`par(mfrow = c(1, 2))`

tells R to show your graphics in a matrix with 1 row and 2 columns, or side-by-side. As always, make sure that your histograms have sensible titles and clear axis labels.

```
library(psych)
library(sm)
red_wine_data = read.table(url("http://assets.datacamp.com/course/Conway/Lecture_Data/L15-16_Wine_Example.txt"), header = T)
ratings_australia = subset(red_wine_data, red_wine_data$condition == "Australia")$Ratings
```

```
## ratings_australia is already loaded
# Print the ratings for the Australian red wine
ratings_australia
# Convert these ratings to Z-scores using the scale() function
z_scores_australia <- ___
# Arrange the histograms side-by-side
par(mfrow = c(1, 2))
# Plot the histogram for the original scores
# Plot the histogram for the Z-scores
```

```
## ratings_australia is already loaded
# Print the ratings for the Australian red wine
ratings_australia
# Convert these ratings to Z-scores using the scale() function
z_scores_australia <- scale(ratings_australia)
# Arrange the histograms side-by-side
par(mfrow = c(1, 2))
# Plot the histogram for the original scores
hist(ratings_australia, main = "Australia red wine ratings", xlab = "score")
# Plot the histogram for the Z-scores
hist(z_scores_australia, main = "Scaled ratings", xlab = "Z-score")
```

```
test_object("z_scores_australia",
incorrect_msg = "It looks like you did not assign the correct Z-scores to <code>z_scores_australia</code>. Use the <code>scale()</code> function to do this. If you don't know how this function works, you can type <code>?scale</code> to get the help file.")
test_function("hist", index = 1, args = c("x"), incorrect_msg = "Did you plot a histogram of the original red wine ratings of Australia?")
test_function("hist", index = 2, args = c("x"), incorrect_msg = "Did you plot a histogram of the Z-scores?")
success_msg("Well done! Take a look at both histograms and make sure that you understand they represent the same data, just on a different scale.")
```