R boxplot: How to customize the appearance of the box-and-whisker plots (e.g., remove lines or borders, change symbol of outliers)

Question

Today, I was wondering how to customize the appearance of the box-and-whisker plots. E.g., I wanted to remove the line around the box. However, the problem is, that the border argument changes the color of all lines of the box-and-whisker plots simultaneously. So, if one has the great idea to set border = "white" then the whiskers are also going to “disappear” and you have a white line representing your median.

As I could not find a solution on the internet dealing with exactly my problem, I fiddled around a little and figured some mighty settings which seem to be nearly undocumented as a whole. These settings allow you to customize the appearance of your box-and-whisker plots to a large extend. I know, some of the features have already been unveiled on stackoverflow (e.g. here). However, I could not find a complete documentation. Thus, this post.

Answer 1

In order to customize the appearance of the box-and-whisker plots, you have to change the med[…], box[…], whisk[…], or staple[…] argument for adjusting the line settings, or the out[…] argument for outliers.

[…] needs to be replaced by one of the following line or point arguments:

Arguments for the appearance of line elements (for more information see ?par in R):

• lty: line style (e.g.,= 0 to remove the line,= 1 for solid line)
• lwd: line width
• col: line color

Arguments for the appearance of outliers (for more information see ?points in R):

• pch: symbol style
• lwd: line width
• cex: size of symbol
• col: color
• bg: background color

So, here is an example of how the above boxplot might be "customized":

boxplot( … , medcol = "red", boxlty = 0, whisklty = 1, staplelwd = 4, outpch = 8, outcex = 3)

This leads to the following boxplot: