Fix computation of dynamic ratio colorbar min/max values

gcpy/plot/six_plot.py
- Now set vmin as the min of the absolute values of the min and max
  of the plot_val array and set vmax as 1/vmin.
- This should prevent the colorbar from being set to a too-narrow range.

CHANGELOG.md
- Updated accordingly.

CHANGELOG.md

@@ -32,6 +32,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Fixed
 - Fixed formatting error in `.github/workflows/stale.yml` that caused the Mark Stale Issues action not to run
 - Now flag differences greater than +/- 10% in benchmark timing table outputs
+- Fixed error in computation of dynamic ratio plot min & max values in `plot/six_plot.py`
 
 ### Removed
 - Removed `gcpy/benchmark/modules/species_database.yml` file and corresponding code pointing to this

gcpy/plot/six_plot.py

@@ -544,10 +544,10 @@ def vmin_vmax_for_ratio_plots(
     """
     # Ratio (dynamic range) subplot)
     if subplot in "dyn_ratio":
-        vmax = np.max(
+        vmin = np.min(
             [np.abs(np.nanmin(plot_val)), np.abs(np.nanmax(plot_val))]
         )
-        vmin = 1.0 / vmax
+        vmax = 1.0 / vmin
         if vmin > vmax:
             vmin, vmax = vmax, vmin
         verbose_print(verbose, rowcol, vmin, vmax)