I created a function to create forest plots, which have labels on the y axis. I need to create a number of them to join in an external graphic program.
The plots images will have the same width but the height will change according to the number of y elements. To achieve this I first created a plot and manually set the image height (i.h1). Then I subtracted from i.h1 the upper (u.m) and bottom (b.m) margin to get the plot height. Finally I divided the plot height by the number of y labels n1 to get the one unit dimension u = (i.h1 - b.m - u.m) / n1.
To get the size of the subsequent image h.i2 I just needed to h.i2 = u * n2 + b.m + u.m.
Here's is the result on a first image with 27 elements (counting the blank spaces) and a second image with 6 elements.
The second image is way higher than what it should be! (the purple lines are for comparison).
Furthermore the internal margin between the lower element and the x axis is different. So even if I use a different unit height I would end up with the labels in the 2 images not aligned.
I don't understand this behavior. Any hint?
Here's the code for saving the picture:
gt <- ggplot_gtable(ggplot_build(plot)) #plot is a ggplot object
gt$layout$clip[gt$layout$name == "panel"] <- "off"
grid.draw(gt)
if (file != F) {
w = 8.5
h = .33 * max(data$yval) + 4 # .33 is the unit height and 4 are the margin
dev.copy(pdf, if (file == T) sprintf("%s.pdf", gsub('\\n', '', title)) else file, width = w, height = h) # I use dev.copy because ggsave don't accept gtable plots.
invisible(dev.off())
}
