Tweaking box plot design

[Shai]

Hi,

Is it possible to manually change the design of the individual
components of a box plot? For example, give different line types/
colors to the median, quantiles, the line that goes to the min/max,
and add a notch to that line.

I know its possible to tweak the design of outliers, so I thought
maybe... :)

Thanks!
Shai

[Brandon Hurr]

I would also like to know this. I saw an S plot this afternoon that had a maroon fill with black 1st and 3rd quartiles with a thick white median. It looked nice and allowed easier comparison of medians and quartiles. 

Brandon

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[Joshua Wiley]

Hi,

I did not see any built-in functionality for this. I kind of like
simple boxplots (maybe with jittered points added), but maybe I'm old
fashioned. Anyway, it is not terribly difficult to add. An example
follows. You can see where all the options go, so if you wanted to
have different colour and style for each, just keep adding arguments
and pass them on.

Cheers,

Josh

# Data
dat <- data.frame(x = 1, y = c(1, 3, 5, 4, 5, 5, 10, 15))
# Default possibilities
ggplot(data = dat, aes(x = x, y = y)) + geom_boxplot(fill = "black",
colour = "maroon", lwd = 2)

# add another argument for the median line colour
GeomBoxplot$draw <- function(., data, ..., outlier.colour = "black",
outlier.shape = 16, outlier.size = 2, midcol = NULL) {
defaults <- with(data, data.frame(
x = x, xmin = xmin, xmax = xmax,
colour = colour, size = size,
linetype = 1, group = 1, alpha = 1,
fill = alpha(fill, alpha),
stringsAsFactors = FALSE
))
defaults2 <- defaults[c(1,1), ]
defaults3 <- defaults
if(is.null(midcol)) {midcol <- defaults[, "colour"]}
defaults3[, "colour"] <- midcol

if (!is.null(data$outliers) && length(data$outliers[[1]] >= 1)) {
outliers_grob <- with(data,
GeomPoint$draw(data.frame(
y = outliers[[1]], x = x[rep(1, length(outliers[[1]]))],
colour=I(outlier.colour), shape = outlier.shape, alpha = 1,
size = outlier.size, fill = NA), ...
)
)
} else {
outliers_grob <- NULL
}

with(data, ggname(.$my_name(), grobTree(
outliers_grob,
GeomPath$draw(data.frame(y=c(upper, ymax), defaults2), ...),
GeomPath$draw(data.frame(y=c(lower, ymin), defaults2), ...),
GeomRect$draw(data.frame(ymax = upper, ymin = lower, defaults), ...),
GeomRect$draw(data.frame(ymax = middle, ymin = middle, defaults3), ...)
)))
}

# Different colours
ggplot(data = dat, aes(x = x, y = y)) + geom_boxplot(fill = "black",
colour = "maroon", lwd = 2, midcol = "white"

--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

[Brandon Hurr]

Very nice Josh. Thanks for the effort. 

Brandon

[Shai]

thanks! I'll try that...