# Generating random numbers

## Problem

You want to generate random numbers.

## Solution

For uniformly distributed (flat) random numbers, use `runif()`

. By default, its range is from 0 to 1.

```
runif(1)
#> [1] 0.09006613
# Get a vector of 4 numbers
runif(4)
#> [1] 0.6972299 0.9505426 0.8297167 0.9779939
# Get a vector of 3 numbers from 0 to 100
runif(3, min=0, max=100)
#> [1] 83.702278 3.062253 5.388360
# Get 3 integers from 0 to 100
# Use max=101 because it will never actually equal 101
floor(runif(3, min=0, max=101))
#> [1] 11 67 1
# This will do the same thing
sample(1:100, 3, replace=TRUE)
#> [1] 8 63 64
# To generate integers WITHOUT replacement:
sample(1:100, 3, replace=FALSE)
#> [1] 76 25 52
```

To generate numbers from a normal distribution, use `rnorm()`

. By default the mean is 0 and the standard deviation is 1.

```
rnorm(4)
#> [1] -2.3308287 -0.9073857 -0.7638332 -0.2193786
# Use a different mean and standard deviation
rnorm(4, mean=50, sd=10)
#> [1] 59.20927 40.12440 44.58840 41.97056
# To check that the distribution looks right, make a histogram of the numbers
x <- rnorm(400, mean=50, sd=10)
hist(x)
```

### Notes

If you want to your sequences of random numbers to be repeatable, see ../Generating repeatable sequences of random numbers.