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## Creating a QQ Plot

### Problem

### Solution

### Discussion

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You want to make a quantile-quantile (QQ) plot to compare an empirical distribution to a theoretical distribution.

Use `qqnorm()`

to compare to a
normal distribution. Give `qqnorm()`

a vector
of numerical values, and add a theoretical distribution line with `qqline()`

(Figure 13-25):

library`(`

gcookbook`)`

`# For the data set`

`# QQ plot of height`

qqnorm`(`

heightweight`$`

heightIn`)`

qqline`(`

heightweight`$`

heightIn`)`

`# QQ plot of age`

qqnorm`(`

heightweight`$`

ageYear`)`

qqline`(`

heightweight`$`

ageYear`)`

The points for `heightIn`

are
close to the line, which means that the distribution is close to normal.
In contrast, the points for `ageYear`

veer far away from the line, especially on the left, indicating that the
distribution is skewed. A histogram may also be useful for exploring how
the data is distributed.