Sample from a Population

We generally require to sample data from a large population. R has a function called sample() to do the same. We need to provide the population and the size we wish to sample. Additionally, we can specify if we want to do sampling with replacement. By default it is done without replacement.

Source Code

> x
[1]  1  3  5  7  9 11 13 15 17

> # sample 2 items from x
> sample(x,2)
[1] 13  9

> # if we don’t provide the size to sample, it defaults to
> # the length of the population. This can be used to scramble x
> sample(x)
[1] 15 11  9 13  3 17  7  5  1

> # sample with replacement
> sample(x, replace=TRUE)
[1] 15 17 13  9  5 15 11 15  1

> # if we simply pass in a positive number n, it will sample
> # from 1:n without replacement
> sample(10)
 [1]  2  4  7  9  1  3 10  5  8  6

> # an example to simulate a coin tossed 10 times
> sample(c("H","T"),10, replace=TRUE)
 [1] "H" "H" "H" "T" "H" "T" "H" "H" "H" "T"