This function draws from a one-sided truncated univariate normal
distribution.

## Usage

`rtnorm(mu, sig, trunpt, above)`

## Arguments

- mu
The mean.

- sig
The standard deviation.

- trunpt
The truncation point.

- above
A boolean, if `TRUE`

truncate from above, otherwise from below.

## Examples

```
### samples from a standard normal truncated at 1 from above
R <- 1e4
draws <- replicate(R, rtnorm(0,1,1,TRUE))
plot(density(draws))
```