A ggplot2 extension for creating normal violin plots with specified means and standard deviations.
You can either install ggnormalviolin from CRAN or install the development version of ggnormalviolin from github.
You can install ggnormalviolin from CRAN by running this code:
install.packages("ggnormalviolin")
To install the development version of ggnormalviolin, you need to check if devtools is installed. If not, run this:
install.packages("devtools")
Once you are sure you have devtools installed, you can install the development version of ggnormalviolin from GitHub by running this code:
devtools::install_github("wjschne/ggnormalviolin")
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).
p + geom_normalviolin(p_tail = 0.05)
Suppose you want to highly only the upper tails. Set p_upper_tail
to
the proportion desired.
p + geom_normalviolin(p_upper_tail = 0.05)
Analogously, you can highlight only the lower tails by setting the
p_lower_tail
parameter.
p + geom_normalviolin(p_lower_tail = 0.05)
The defaults for highlighting is accomplished by selecting a subset of
the whole distribution, setting tail_fill
to black, and 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
.
p + geom_normalviolin(face_left = FALSE)
p + geom_normalviolin(
face_right = FALSE,
p_tail = 0.05)
You can set the width
of the violin to any size desired.
p + geom_normalviolin(width = 1)
If you want the shape of the distribution to remain constant, map the
width
parameter to a multiple of the standard deviation.
p + geom_normalviolin(aes(width = dist_sd * 0.05))
By default, the normal violins extend 4 standard deviations in both
directions. Use the nsigma
parameter to set a different value.
p + geom_normalviolin(nsigma = 1.5)
If you set limits on the y scale, it is possible that some of the violins will be distorted or cut in pieces.
p +
geom_normalviolin() +
ylim(50,140)
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).
p +
geom_normalviolin(lower_limit = 50, upper_limit = 140) +
ylim(50,140)
Alternately, you can set the limits in ggplot2::coord_cartesian
, which
will zoom the plot instead of discarding the data.
p +
geom_normalviolin() +
coord_cartesian(ylim = c(50, 140))
Please note that the ‘ggnormalviolin project’ is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.
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