A ggplot2 extension for creating normal violin plots with specified means and standard deviations.

To install the development version of ggnormalviolin, you need to check if devtools is installed. If not, run this:

Once you are sure you have devtools installed, you can install the development version of ggnormalviolin from GitHub by running this code:

Suppose there are 4 hypothetically normal distributions with specific means and standard deviations. They can be plotted like so:

```
library(ggplot2)
library(ggnormalviolin)
# Make data
d <- data.frame(
dist = c("A", "B", "C", "D"),
dist_mean = c(80, 90, 110, 130),
dist_sd = c(15, 10, 20, 5)
)
# Make base plot
p <- ggplot(data = d,
aes(x = dist,
mu = dist_mean,
sigma = dist_sd,
fill = dist)) +
theme(legend.position = "none")
# Add normal violins
p + geom_normalviolin()
```

Suppose you want to highlight the two tails of the distributions. Set the `p_tails`

to specify the total area of the tails. Thus, if `p_tail`

= 0.05, each tail will represent the outermost 2.5% of the distributions (i.e, 0.05 = 2 &mult; 0.025).

Suppose you want to highly only the upper tails. Set `p_upper_tail`

to the proportion desired.

Analogously, you can highlight only the lower tails by setting the `p_lower_tail`

parameter.

The defaults for highlighting is accomplished by selecting a subset of the whole distribution, setting `tail_fill`

to black, and making the then making the black fill transparent by setting `tail_alpha`

= 0.4. Setting these values to other colors and levels of transparency can dramatically change the look of the plot.

```
p + geom_normalviolin(
p_tail = 0.05,
tail_fill = "white",
tail_alpha = 0.8,
color = "gray20",
size = 0.1
)
```

If you want to omit the left or right side of the violins, you can set the `face_left`

or `face_right`

parameters to `FALSE`

.

You can set the `width`

of the violin to any size desired.

If you want the shape of the distribution to remain constant, map the `width`

parameter to a multiple of the standard deviation.

By default, the normal violins extend 4 standard deviations in both directions. Use the `nsigma`

parameter to set a different value.

If you set limits on the y scale, it is possible that some of the violins will be distorted or cut in pieces.

This occurs because data outside the limits is discarded, breaking up the polygons that compose the violins into smaller pieces. To prevent such behavior, set the `upper_limit`

and `lower_limit`

parameters equal to the same limits you have specified for the y scale (or any other values you wish).

Alternately, you can set the limits in `ggplot2::coord_cartesian`

, which will zoom the plot instead of discarding the data.

Please note that the â€˜ggnormalviolin projectâ€™ is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.