Using a function and variable column within ggplot

Question

I want to make a ggplot call variable to the user, without changing the ggplot call in the script...

I have a data frame with different columns I would love to use for label the dots on my plot. A lot of those columns are long and I want to provide a function 'shortname' to shorten the column a bit...

I also want to make this variable with a variable and this is where I stuck at the moment.

df <- data.frame(a=c('a;b;c','d;e;f'), b=c('A;B;C','D;E;F'),
                 x=c(1,2), y=c(2,3))

use_column <- 'b'
shortname <- function(x) {
  sub('([^;]+).*', '\\1', x)
}

g <- ggplot(df, aes(x,y)) + geom_point()
g + geom_text(aes(label=a))
g + geom_text(aes(label=shortname(a)))
g + geom_text(aes(label=shortname(b)))

Up to this point, everything works as expected. The first plots shows column a shortened and the second plot shows column b. But when I try to use the variable use_column, I don't get it to run...

g + geom_text(aes_string(label=shortname(use_column)))

I am running out of ideas and hope somebody can help me on this.

Thanks in advance!

shadow · Accepted Answer · 2015-02-17 11:17:59Z

1

The problem is that you use shortname on b, which returns b. Only then does the aes_string read the resulting b and uses the whole b for evaluating.

You can avoid this by using "shortname(b)" instead of shortname("b"). That is

g + geom_text(aes_string(label=paste('shortname(', use_column, ')')))

Alternatively, you could use aes together with get.

g + geom_text(aes(label=shortname(get(use_column))))

edited Feb 17, 2015 at 11:17

answered Feb 17, 2015 at 7:58

shadow

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1 Comment

drmariod Over a year ago

Huh, this is still hard to read... Is there a way to make it more readable with aes()... I just used aes_string() during some testing... But at least it is a working solution, thanks for this!

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