ggsave is confusing

[Marc Pabst (marcpabst)]

Is there a good way to make sure that

• (a) my plot actually ends up being the apsect ratio I set using the w and h paramters of ggsave, and
• (b) my 15pt font size is actually 15pt in an exported PDF?

So far, my plot adheres to dome magic, pre-set aspect ratio and I end up with lots of white space in my PDF. I can use ggsize to change that, but that screws up the scaing.

[Igor Alshannikov (alshan)]

Yes, you are supposed to control the plot's aspect ratio by setting its absolute size in pixels using ggsize(). What's happening with the scaling?

[Marc Pabst (marcpabst)]

It's a bit unclear how pixels in ggsize relate to physical units in gsave. I would have assumed that you can control that via the dpi paramter, but that seems to do nothing. I think per default, 72px = 1inch?

[Igor Alshannikov (alshan)]

Maybe 1 pixel = 1/96th as was mentioned in this discussion: #839
But we actually don't do this conversion directly. We only create the plot SVG (where the size is in pixels) and then pass it to Cairosvg (along with the desired dimensions in inches) to generate PNG or PDF.

UPD: we also pass provided DPI to CairoSVG so I'm pretty sure the px/inch ratio is controlled by the DPI.

[Igor Alshannikov (alshan)]

We've updated the ggsave() documentation (see Notes) and related cookbook here (see "Parameters w, h, unit, and dpi" section).
I hope this address this issue well.