Excessive whitespace in saved images from sp::plot()

After messing around with parameters aimlessly I managed to solve my
problem.

The key seems to be that par(mar=c(0, 0, 0, 0)) needs to come AFTER
png('plot.png')
as in:
png('plot.png')
par(mar=c(0, 0, 0, 0))
plot(square, axes = F, lwd = 2, asp = "", xpd = NA)
dev.off()

I have no idea why this is the case, but it works!

M

On Tue, Dec 15, 2015 at 2:22 PM, Matt Strimas-Mackey <strimas at zoology.ubc.ca

wrote:

Thanks for the suggestions.

Here's what I tried based on what you said:
par(mar=c(0, 0, 0, 0))
png('plot.png')
plot(square, axes = F, lwd = 2, asp = "", xpd = NA)
dev.off()

Unfortunately, this didn't make any difference...  Any other thoughts?


Thanks!

M

On Tue, Dec 15, 2015 at 11:48 AM, Michael Sumner <mdsumner at gmail.com>
wrote:

Try changing the aspect ratio, asp="" from memory to 'fill the device'.
You might also need par(xpd=NA) or similar to remove the axis buffering.

R and sp generally plot within a figure space, rendering to a "world
space" within a file is not directly supported (writeGDAL and writeRaster
do this, but not for rendering 'layers'). But with careful handling you can
do it.

I think external georeferencing would be required for downstream spatial
use, but I am hoping to be corrected on that point(?)

Cheers, Mike


On Wednesday, December 16, 2015, Matt Strimas-Mackey <
strimas at zoology.ubc.ca> wrote:

I'm trying to plot simple SpatialPolygons objects using the basic
plot() command from sp and save these as png or svg. For context, this
is part of a rmarkdown report that will eventually go on the web, so
the saving of images will be done automatically via knitr. Since this
involves images, I've put the code and images online:

https://github.com/mstrimas/mstrimas.github.io/tree/master/_source/print-problems

My problem is excessive whitespace around the plots:

library(sp)
par(mar=c(0, 0, 0, 0))
png('png-dev-400x400.png', width = 400, height = 400)
plot(square, axes = F)
dev.off()

But only when saving with a direct call to png() or svg(). Plotting,
then saving interactively via RStudio or with

dev.print(png, 'dev-print-400x400.png', width = 400, height = 400)

yields a nice plot with no whitespace.

I only encounter this problem when plotting spatial objects, which is
why I'm posting here. Since these are simple polygons with no
attributes, I'd prefer to avoid using spplot(). Also, I've tried this
on 2 machines: a Mac and a PC running Ubuntu, in both cases running
the latest version of R and the sp package.

Thanks!

M

--
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com

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