R pdf() usage inside a function()

Question

I have some code in R that generates a multipage pdf file:

pdf("myplot.pdf", width=8.5, height=5)

My.Plot(my.data, var1, var2)
My.Plot(my.data, var3, var2)
My.Plot(my.data, var4, var2)

dev.off()

My.Plot() is just a function that parses the necessary data and then uses ggplot to create a graph

The above works just fine. However, when I put this code in a function, there are no plots generated and the output PDF can not be read/opened.

generate.PDF <- function(my.data) {    
    pdf("myplot.pdf", width=8.5, height=5)

    My.Plot(my.data, var1, var2)
    My.Plot(my.data, var3, var2)
    My.Plot(my.data, var4, var2)

    dev.off()
}

Answer 1

When in a function, you need to call the print() function to actually paint on the canvas, like so:

x <- runif(20,10,20)
y <- runif(20,30,50)
data<-data.frame(x,y)
generate.PDF <- function(data) {    
  pdf("/home/aksel/Downloads/myplot.pdf", width=8.5, height=5,onefile=T)
  plot1 <- plot(x,y)
  plot2 <- plot(y,x)
  plot3 <- plot(x,y*2)
  print(plot1)
  print(plot2)
  print(plot3)
  dev.off()
}
generate.PDF(data)