 Distributions in R - dummies

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.

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.