## random-sample

2021-12-30

Random sample of a sequence with uniform distribution.

### Upstream URL

### Author

Paul M. Rodriguez <pmr@ruricolist.com>

### License

MIT

Random-Sample is a Lisp library for something which is not nearly as simple as it sounds: reliably taking a random sample of a sequence.

Most of the time you will just use `random-sample`

:

```
(random-sample:random-sample (iota 100) 5)
=> (57 32 28 45 4)
```

The algorithm used for sampling without replacement is basically Vitter’s Algorithm D.

Sometimes you may want to use the algorithm at a lower level. You
don’t want the sample itself; you only want the indices. In this case,
you can directly use `map-random-below`

, which simply calls a provided
function on each index.

```
(map-random-below my-function 5 length)
```