Problem

You want to compare the distribution of your data to another distribution. This is often used to check whether a sample follows a normal distribution, to check whether two samples are drawn from the same distribution.

Solution

Suppose this is your data:

set.seed(183)
# Normally distributed numbers
x <- rnorm(80, mean=50, sd=5)

# Uniformly distributed numbers
z <- runif(80)

# Compare the numbers sampled with rnorm() against normal distribution
qqnorm(x)
qqline(x)

# The same numbers to the 4th power, compared to the normal distribution
qqnorm(x^4)
qqline(x^4)


# Numbers sampled from the flat distribution, compared to normal
qqnorm(z)
qqline(z)

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