ggplot + powerpoint = wall + head … solution?

September 2, 2013
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(This article was first published on Matt's Stats n stuff » R, and kindly contributed to R-bloggers)

Confession, by ‘solution?’ I literally mean I’m asking for your thoughts on a solution.

Like it or lump it I do a lot of graphs for presentations, largely in powerpoint. That’s the way my colleagues/industry work(s) and it’s not about to change anytime soon. I have a real frustration with getting my plots out and into powerpoint.

What am I after?

A good workflow for exporting plots, the same dimensions each time, so that tick mark text, axis labels etc are readable and the plots are nice and sharp. I want the plot to take up about 75% of the slide (so leaving enough room for a heading). I want to be able to drag and drop the plots from a folder onto the slide.

What have I done in the past?

Numerous different things. Sometimes if it’s got to be done quick I’ll use the export in Rstudio and quickly resize. Or I’ll zoom in on Rstudio (resizing) and take a screenshot (v easy with a mac but the naming is naff). Or I’ll export them using a function and then resize within powerpoint. But THAT is what I am trying to avoid (well, perfect). Why, because it’s a pain. Because it’s inconsistent. If I am changing slides from a plot of males to a plot of females, I want the plot to be the EXACT same size sitting in the exact same spot on the next slide. Nothing irritates me more than plots bouncing around from slide to slide. And this is difficult and time consuming to do and get right within ppt.

Where am I up to with a workflow?

This is where I’m hoping someone can set me on the straight and narrow. I’m looking at ggsave and png/dev.off as two options. What works well on the slide is a png that is about 400×400 pixels . This is 5.56×5.56 inches or 14.11×14.11cm at 72 dpi. That drops nicely on a slide leaving enough room for a heading.

With ggsave you can’t specify size in pixels(?), hence providing the values in the other units.

Where I have hit a wall is the ratio of text to plot size. ggsave seems to have things nice and sharp, but altering ‘scale’ or ‘dpi’ (no surprises based on their intention) changes the actual ‘size on the slide’ of the plot, given that ppt has to show it at 72 dpi. The problem with ggsave is that with w/h 14.11cm and dpi 72 then the size is right but it’s not sharp. png/dev.off has the same problem. When I set w/h to 14.11cm and dpi to 300 the actual image (when at 72 dpi) is ~55cm. And powerpoint has to display it at 72 dpi, so it blows off the page.

What does kinda work?

If I create an image using ggsave w/h 14.11cm and dpi 300, open it in preview on the mac, it says that at 72 dpi it is ~55cm, I can then resize it down to 14.11cm (with the ‘resample image’ option UNchecked), I then get an image that is 14.11cm that is nice and sharp and drops into powerpoint nicely.

Question!

Is there a way to get R to resample the image on the way out? Is there a better way to do this (has to be!)? Would creating a theme where everything is smaller benefit the situation (I tend to think not).

I feel like I’m going about this all the wrong way. But, given that the ‘what does kinda work?’ above actually does get a nice sharp plot to just drag and drop onto the page, that means it is possible and it’s just about the workflow right, right?


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