using function on colum name with aes_string in ggplot graph

Question

I want to plot some graphs and the column name is changing within a loop. I also want to apply a log2() onto this column so my plan was to do something like this:

df <- data.frame(x=c(1,2,3,4,5),
                 y.bla=c(2,3,4,5,6),
                 y.blub=c(5,4,3,2,1))
for(label in c('bla','blub')) {
  g <- ggplot(df, aes_string(x='x', y=paste0('y.', label))) + geom_point()
  print(g)
}

for(label in c('bla','blub')) {
  g <- ggplot(df, aes_string(x='x', y=log2(paste0('y.', label)))) + geom_point()
  print(g)
}

But actually, the log2 function can not handle the string.
Is there a workaround?

I want to do this within the loop and not with facet wrap or something like this, since I append these single graphs to a list of different figures.

Mhairi McNeill · Accepted Answer · 2015-07-15 11:39:21Z

2

There's probably a few ways of doing this. I'd extract elements from the dataframe by name and transform them before plotting.

for(label in c('bla','blub')) {

  temp_var <- log2(df[[paste0('y.', label)]])

  g <- ggplot(df, aes(x=x, y= temp_var)) + geom_point()
  print(g)
}

answered Jul 15, 2015 at 11:39

Mhairi McNeill

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1 Comment

drmariod Over a year ago

Hah, that was to easy! I expected R will complain because it is no data frame or something... Love it!

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