R help - Feb 2024 - Extracting Plot Arguments

Hi All,

I'm building an autograding framework for my biostatistics class this
semester, and I am exploring different ways to automatically grade
figures.

In other classes, I teach ggplot2 and I extract information directly
from the ggplot2 object. However, in this class we are using base R
and I need to extract information from base-r graphics.

I've tried several different approaches, but I'm not sure which one is
the easiest and most effective. Has anyone ever tried this? Are there
any packages to help with this?

(1) Storing `recordedplots` objects and trying to extract information
from them. This data structure felt very low level, and I wasn't sure
how easy it was to map the results to user-level function calls.

(2) Use the `svglite` device to produce svg files, which can be
parsed. This also worked, but required a lot of code to parse the
resulting images and identify things like labels, and coordinate
locations. I got tired of having to figure how to extract information
from an SVG.

(3) Use a wrapper on specific graphics functions that records the
function arguments. This turns out to be a bit too high level, as I
have to manually massage inputs. E.g. handle both xy plots and formula
+ data plots. (We teach both styles.)

Are there any other ideas that I can try? My students are using an
RMarkdown worksheet and answering questions by putting code in
specific chunks. I've already hooked into knitr so I can record the
chunk lines as they are being run and  get the results and
side-effects.

Thanks,
Reed

--
Reed A. Cartwright, PhD
Associate Professor of Genomics, Evolution, and Bioinformatics
School of Life Sciences and The Biodesign Institute
Arizona State University
=================Address: The Biodesign Institute, PO Box 876401, Tempe, AZ
85287-6401 USA
Packages: The Biodesign Institute, 1001 S. McAllister Ave, Tempe, AZ
85287-6401 USA
Office: Biodesign B-220C, 1-480-965-9949
Website: http://cartwrig.ht/

Does the grid.echo function in the gridGraphics package do what you want?

Description
Convert a scene that was drawn using the graphics package to an identical scene
drawn with the
grid package.
> On Feb 21, 2024, at 22:49, Reed A. Cartwright <racartwright at
gmail.com> wrote:
>
> Hi All,
>
> I'm building an autograding framework for my biostatistics class this
> semester, and I am exploring different ways to automatically grade
> figures.
>
> In other classes, I teach ggplot2 and I extract information directly
> from the ggplot2 object. However, in this class we are using base R
> and I need to extract information from base-r graphics.
>
> I've tried several different approaches, but I'm not sure which one
is
> the easiest and most effective. Has anyone ever tried this? Are there
> any packages to help with this?
>
> (1) Storing `recordedplots` objects and trying to extract information
> from them. This data structure felt very low level, and I wasn't sure
> how easy it was to map the results to user-level function calls.
>
> (2) Use the `svglite` device to produce svg files, which can be
> parsed. This also worked, but required a lot of code to parse the
> resulting images and identify things like labels, and coordinate
> locations. I got tired of having to figure how to extract information
> from an SVG.
>
> (3) Use a wrapper on specific graphics functions that records the
> function arguments. This turns out to be a bit too high level, as I
> have to manually massage inputs. E.g. handle both xy plots and formula
> + data plots. (We teach both styles.)
>
> Are there any other ideas that I can try? My students are using an
> RMarkdown worksheet and answering questions by putting code in
> specific chunks. I've already hooked into knitr so I can record the
> chunk lines as they are being run and  get the results and
> side-effects.
>
> Thanks,
> Reed
>
> --
> Reed A. Cartwright, PhD
> Associate Professor of Genomics, Evolution, and Bioinformatics
> School of Life Sciences and The Biodesign Institute
> Arizona State University
> =================> Address: The Biodesign Institute, PO Box 876401,
Tempe, AZ 85287-6401 USA
> Packages: The Biodesign Institute, 1001 S. McAllister Ave, Tempe, AZ
> 85287-6401 USA
> Office: Biodesign B-220C, 1-480-965-9949
> Website: http://cartwrig.ht/
>
> ______________________________________________
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