Iteratively changing the y-axis label in a series of plots

[dha 2001]

Hi,

This one is probably easy but I have not been able to sort it out
after a few weeks of trying on and off.

I'm having trouble figuring out how to update the y-axis label on a
series of plots generated in a loop. I've included a toy example
below which illustrates the issue. The actual code I'm working with
creates a moderately complex arrangement of plots on a pdf page. I
have a list of variables and want to create the same arrangement on a
series of pages, one for each of the variables in the list. I've
removed the pdf generating code here so it makes little sense on the
screen but illustrates the issue.

I can iterate the data and even the title of each plot just fine but
not the y-axis. The title of the y-axis ends up as "get(yVar)".

library(ggplot2)

variables=c("drat","qsec")
basePlot <- ggplot(mtcars, aes( x=wt, y=qsec)) +
geom_point()

for (yVar in variables) {
newPlot <- basePlot + aes(y=get(yVar)) + # axis label doesn't work
opts(title=yVar) + # works.
opts(axis.title.y=get(yVar))
print(newPlot)
}


I have tried adding the following to "newPlot" with no success:

+ opts(axis.title.y=yVar)
Error in grobName(grob, prefix) : Invalid 'grob' argument

+ opts(axis.title.y=deparse(yVar))
Error in grobName(grob, prefix) : Invalid 'grob' argument

+ opts(axis.title.y=get(yVar))
Error in get(yVar) : object 'drat' not found

Any help would be greatly appreciated!

[Dennis Murphy]

Hi:

Try this:

library('ggplot2')

variables=c("drat","qsec")

for (yVar in variables) {
print(ggplot(mtcars, aes_string(x = 'wt', y= yVar)) +
geom_point() +
opts(title=yVar)
)
}

aes_string() is used to pass a character string as values of the x and
y arguments. For the main title, the value of the title argument is a
character string, so you're covered there.

HTH,
Dennis

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[dha 2001]

Thanks! That did it.