Komal Rathi - 7 months ago 73

R Question

I have created a boxplot using ggplot2:

`library(ggplot2)`

dat <- data.frame(study = c(rep('a',50),rep('b',50)),

FPKM = c(rnorm(1:50),rnorm(1:50)))

ggplot(dat, aes(x = study, y = FPKM)) + geom_boxplot()

The boxplot shows the median as a horizontal line across each box.

How do I add a dashed line to the box representing the mean of that group?

Thanks!

Answer

You can add horizontal lines to plots by using `stat_summary`

with `geom_errorbar`

. The line is horizontal because the y minimum and maximum are set to be the same as y.

```
ggplot(dat, aes(x = study, y = FPKM)) +
geom_boxplot() +
stat_summary(fun.y = mean, geom = "errorbar", aes(ymax = ..y.., ymin = ..y..),
width = .75, linetype = "dashed")
```