Use two-digit identifier for generated figures

[gvwilson]

@fmichonneau writes:

For the fig path, I think it has been inconsistent. Personally, I
think it's a good idea to given figures a prefix for each episode, so
we can see right away where the figures are coming from (and whether
some need to be deleted if they are not in use anymore). Therefore, in
the gapminder lesson, I set as a prefix the 2 digit number for the
episode (even if the lesson doesn't generate a figure), so each
episode should start with something like:

    ```{r, include=FALSE}
    source("../bin/chunk-options.R")
    knitr_fig_path("01-")
    ```

1. Make this change to all .Rmd files.
2. Clean out all old figures.

See also swcarpentry/r-novice-inflammation#217

[fmichonneau]

Just to clarify, as it stands, all Rmd files in _episodes_rmd for this lesson already have their fig path set this way, and I think that I removed all the figures that are not in use (but this should be double checked).

[gvwilson]

make lesson-check in the root directory warns me about two R files in
the fig directory:

Unexpected image files: 13-dplyr-generate-figures.R, 
14-tidyr-generate-figures.R

[fmichonneau]

I'll also try to write the blog post about the details of using Rmd files with the new template today or Friday.

[gvwilson]

Yay!

[chendaniely]

has this issue been resolved?

I see the following when I look at ls *

fig:
01-supp-csv-without-row-nums.png  python-call-stack-07.svg                               rmd-02-func-R-rescale-test-2.png      rmd-03-loops-R-loop-analyze-3.png             rmd-04-cond-conditional-challenge-hist-3.png  rmd-12-supp-factors-reordering-factors-1.png
01-supp-csv-with-row-nums.png     python-flowchart-conditional.svg                       rmd-03-loops-R-inflammation-01-1.png  rmd-03-loops-R-loop-analyze-4.png             rmd-04-cond-inflammation-01-1.png             rmd-12-supp-factors-updating-factors-1.png
01-supp-csv-with-special-NA.png   python-sticky-note-variables-01.svg                    rmd-03-loops-R-inflammation-01-2.png  rmd-03-loops-R-loop-analyze-5.png             rmd-04-cond-inflammation-01-2.png             rmd-logical_vectors_indexing2-1.png
python-call-stack-01.svg          python-sticky-note-variables-02.svg                    rmd-03-loops-R-inflammation-01-3.png  rmd-03-loops-R-loop-analyze-6.png             rmd-04-cond-inflammation-01-3.png             r-operations-across-axes.svg
python-call-stack-02.svg          python-sticky-note-variables-03.svg                    rmd-03-loops-R-inflammation-02-1.png  rmd-03-loops-R-loop-analyze-7.png             rmd-04-cond-using-conditions-01-1.png
python-call-stack-03.svg          rmd-01-starting-with-data-plot-avg-inflammation-1.png  rmd-03-loops-R-inflammation-02-2.png  rmd-03-loops-R-loop-analyze-8.png             rmd-04-cond-using-conditions-01-2.png
python-call-stack-04.svg          rmd-01-starting-with-data-plot-max-inflammation-1.png  rmd-03-loops-R-inflammation-02-3.png  rmd-03-loops-R-loop-analyze-9.png             rmd-12-supp-factors-adjusting-levels-1.png
python-call-stack-05.svg          rmd-01-starting-with-data-plot-min-inflammation-1.png  rmd-03-loops-R-loop-analyze-1.png     rmd-04-cond-conditional-challenge-hist-1.png  rmd-12-supp-factors-dropping-levels-1.png
python-call-stack-06.svg          rmd-02-func-R-rescale-test-1.png                       rmd-03-loops-R-loop-analyze-2.png     rmd-04-cond-conditional-challenge-hist-2.png  rmd-12-supp-factors-gender-counts-1.png

[fmichonneau]

Yes, I believe that I added the correct prefix for the figures for each lesson. There might be some leftovers figures though.

[naupaka]

Closing for now, feel free to re-open if problem is noticed elsewhere.