Merge pull request #819 from sadielbartholomew/student-recipes-2

Add new recipe (17) by summer student: colourmap subplots

Author: sadielbartholomew

docs/source/recipes/plot_17_recipe.py

@@ -0,0 +1,114 @@
+"""
+Plotting contour subplots with different colour maps/scales
+===========================================================
+
+In this recipe, we will plot the same data with different colour maps from
+three categories in separate subplots to illustrate the importance of
+choosing a suitable one for given data. To avoid unintended bias and
+misrepresentation, or lack of accessibility, a careful choice must be made.
+"""
+
+# %%
+# 1. Import cf-python and cf-plot:
+
+import cfplot as cfp
+import matplotlib.pyplot as plt
+
+import cf
+
+# %%
+# 2. Read the field in:
+f = cf.read("~/recipes/ggap.nc")[0]
+
+# %%
+# 3. Choose a set of predefined colour scales to view. These can be chosen
+# from the selection at:
+# https://ncas-cms.github.io/cf-plot/build/colour_scales.html or you
+# can define your own, see:
+# https://ncas-cms.github.io/cf-plot/build/colour_scales.html#user-defined-colour-scales.
+# Here we take three colour scales each from three different general
+# categories, to showcase some differences in representation.
+# Note colour scale levels can be adjusted using 'cscale' and keywords such as:
+# cfp.cscale(<cmap name>, ncols=16, below=2, above=14)
+
+# %%
+# a. Perceptually uniform colour scales, with no zero value, see:
+# https://ncas-cms.github.io/cf-plot/build/colour_scales.html#perceptually-uniform-colour-scales.
+colour_scales_pu = ["viridis", "magma", "plasma"]
+
+# %%
+# b. NCAR Command Language colour scales enhanced to help with colour
+# blindness, see:
+# https://ncas-cms.github.io/cf-plot/build/colour_scales.html#ncar-command-language-enhanced-to-help-with-colour-blindness.
+# These colour maps are better for accessibility.
+colour_scales_ncl = ["posneg_1", "GreenMagenta16", "StepSeq25"]
+
+# %%
+# c. Orography/bathymetry colour scales, see:
+# https://ncas-cms.github.io/cf-plot/build/colour_scales.html#orography-bathymetry-colour-scales.
+# These are used to show the shape/contour of land masses, but bear in mind the
+# data we show here is air temperature so doesn't represent this and
+# therefore it is not a good choice in this case:
+colour_scales_ob = ["wiki_1_0_2", "wiki_2_0", "wiki_2_0_reduced"]
+
+
+# %%
+# 4. We plot each category of colourmap in a given columns of the subplot,
+# but given the 'gpos' function positions subplots from left to right, row by
+# row from the top, we need to interleave the values in a list. We can use
+# zip to do this:
+colour_scales_columns = [
+    cscale
+    for category in zip(colour_scales_pu, colour_scales_ncl, colour_scales_ob)
+    for cscale in category
+]
+
+
+# %%
+# 5. Create the figure and give it an overall title. Ensure the
+# number of rows * number of columns = number of colour scales:
+cfp.gopen(rows=3, columns=3, bottom=0.1, top=0.85)
+plt.suptitle(
+    (
+        "Air temperature (K) at 850 mbar pressure shown in different "
+        "categories of colour scale"
+    ),
+    fontsize=18,
+)
+
+# %%
+# 6. We loop through all the different colour maps defined and plot
+# as subplots, with each category in the same column, labelling each column
+# with the colour scale category:
+for i, colour_scale in enumerate(colour_scales_columns):
+    cfp.gpos(i + 1)
+    cfp.cscale(colour_scale)
+
+    # For the topmost plots, label the column with the colour scale category
+    # using the 'title' argument, otherwise don't add a title.
+    # Ensure the order the titles are written in corresponds to the
+    # order unzipped in step 4, so the columns match up correctly.
+    if i == 0:
+        set_title = "Perceptually uniform\ncolour maps"
+    elif i == 1:
+        set_title = (
+            "NCL colour maps enhanced to \nhelp with colour blindness"
+        )
+    elif i == 2:
+        set_title = "Orography/bathymetry\ncolour maps"
+    else:
+        set_title = ""
+
+    cfp.con(
+        f.subspace(pressure=850),
+        title=set_title,
+        lines=False,
+        axes=False,
+        colorbar_drawedges=False,
+        colorbar_title=f"Shown in '{colour_scale}'",
+        colorbar_fraction=0.04,
+        colorbar_thick=0.02,
+        colorbar_fontsize=11,
+    )
+
+cfp.gclose(view=True)

docs/source/recipes/recipe_list.txt

@@ -29,4 +29,6 @@ plot_14_recipe.html#sphx-glr-recipes-plot-14-recipe-py
 plot_15_recipe.html#sphx-glr-recipes-plot-15-recipe-py
 <div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Histogram, Subspace, Subplot">
 plot_16_recipe.html#sphx-glr-recipes-plot-16-recipe-py
+<div class="sphx-glr-thumbcontainer histogram subspace" tooltip="Histogram, Subspace">
+plot_17_recipe.html#sphx-glr-recipes-plot-17-recipe-py
 <div class="sphx-glr-thumbcontainer contourmap subspace subplot" tooltip="Contourmap, Subspace, Subplot">