# Distributions in R

The normal distribution family is one of many distribution families baked into R. Dealing with these families is intuitive. Follow these guidelines:

- Begin with the distribution family’s name in R (norm for the normal family, for example).
- To the beginning of the family name, add
`d`

to work with the probability density function. For the probability density function for the normal family, then, it’s`dnorm()`

. - For the cumulative density function (cdf ), add
`p (pnorm()`

, for example). - For quantiles, add
`q (qnorm()`

, which in mathematical terms is the*inverse*of the cdf ). - To generate random numbers from a distribution, add
`r`

. So`rnorm()`

generates random numbers from a member of the normal distribution family.

The complex relationship between x and f(x) is

If you supply values for μ (the mean), Σ (the standard deviation), and *x* (a score), the equation gives you back a value for *f(x),* the height of the normal distribution at *x.* π and *e* are important constants in mathematics: π is approximately 3.1416 (the ratio of a circle’s circumference to its diameter); *e* is approximately 2.71828. It’s related to something called natural logarithms and to numerous other mathematical concepts.