Plots the probability distribution function of a beta variable from the
mean and standard deviation in either transformed (logit) or untransformed space.

`plot_betavar(m, sd, label = NULL, is_logit = FALSE, color = "black")`

## Arguments

- m
A vector of means of the distribution.

- sd
A vector of standard deviations of the distribution.

- label
Name of the variable to be used as x-axis label.

- is_logit
Logical that indicates whether the means and standard deviations are in
logit (TRUE) or normal (FALSE) space.

- color
A vector of colors.

## Value

A plot of the probability distribution function. Vertical dotted line
indicates mean of distribution. This function can plot multiple curves when multiple means
and standard deviations are provided.

## Examples

```
mu <- 0.5
stddev <- 0.1
plot_betavar(mu, stddev) # mean of plot should be 0.5
#logit parameters
mu <- 0
stddev <- 0.1
plot_betavar(mu, stddev, is_logit = TRUE) # mean of plot should be 0.5
```