r - gridsvg does not work when used inside a function -

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i want define plot saving function uses gridsvg device package gridsvg.

library(ggplot2) library(gridextra)     mtcars$gear <- factor(mtcars$gear,levels=c(3,4,5),                       labels=c("3gears","4gears","5gears"))  mtcars$am <- factor(mtcars$am,levels=c(0,1),                     labels=c("automatic","manual"))  mtcars$cyl <- factor(mtcars$cyl,levels=c(4,6,8),                      labels=c("4cyl","6cyl","8cyl"))   myplot <- qplot(mpg, data=mtcars, geom="density", fill=gear, alpha=i(.5),         main="distribution of gas milage", xlab="miles per gallon",         ylab="density")  saveplot <- function(filename, plot, plotwidth = 15, plotheight = 10){     gridsvg:::gridsvg(name = filename, width = plotwidth, height = plotheight)     print(plot)     dev.off(which = dev.cur()) }

however if try use function not work. error results:

saveplot("~/desktop/myplot.svg", myplot)  show traceback   rerun debug  error in eval(expr, envir, enclos) : object 'filename' not found

however if steps console works:

gridsvg::gridsvg(name = "~/desktop/myplot.svg", width = 15, height = 10) myplot dev.off()

is there way might able use gridsvg function within function?

i wonder if might able eval environment.

thanks, ben.

here's roundabout, more principled, way without sticking in global environment (inspired scoping discussion in r inferno):

library(gridsvg)  saveplot <- function(filename, plot, plotwidth = 15, plotheight = 10){     gridsvg(sys.frame(1))     print(plot)     grid.export(filename)     grdevices::dev.off(which = dev.cur()) }

sys.frame(1) gives evaluation frame of parent context (there's ok explanation here variations on functions access call stack).

i separated out call grid.export() call dev.off(), because dev.off gridsvg call grid.export, call grdevices::dev.off. lets explicitly feed file name grid.export.


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