# Random Numbers and Seeds in R

To explore how R generates random numbers, we will use the `rnorm`

function. This function draws a random number from a normal distribution with a mean = 0 and standard deviation = 1 (though these can be changed with the `mean`

and `sd`

parameters). With `n = 1`

we will get one random number.

`rnorm(n = 1)`

`## [1] 1.992159`

`rnorm(n = 1)`

`## [1] -0.2411932`

Each time you run the command you will get a different number. The `set.seed`

function will sets a seed to the random number generator so that each subsequent run will produce the same number.

`set.seed(2112); rnorm(n = 1)`

`## [1] 0.9243372`

`set.seed(2112); rnorm(n = 1)`

`## [1] 0.9243372`

Setting a different seed results in a different number.

`set.seed(2113); rnorm(n = 1)`

`## [1] 0.5499032`

**What are seeds?**

Computers are actually bad at random events. However, there are good algorithms that mimic random processes (hence psydo random). These algorithms work by starting with some initial value, a seed, and executing a complex algorithm that approximates randomization. The seed is often set to the current time in milliseconds. To visualize the random process, we will use the `sample`

function to randomly select a number between 1 and 100. We will consider the ouput for the first 1,000 seeds.

```
random_numbers <- integer(1000)
for(i in seq_len(length(random_numbers))) {
set.seed(i)
random_numbers[i] <- sample(1:100, size = 1)
}
library(ggplot2)
ggplot(data.frame(x = 1:100, y = random_numbers),
aes(x = x, y = y)) +
geom_point() +
xlab('Seed') + ylab('Random Number')
```