Add Natalia's recipe to showcase plotting projections

Author: Natalia Hunt

docs/source/recipes/plot_16_recipe.py

@@ -0,0 +1,59 @@
+"""
+Plotting Contour Subplots with different Projections
+============================================
+In this recipe, we will plot different projections for the same data to illustrate
+visually the ones available in order to more visually decide which is suitable.
+"""
+
+# %%
+# 1. Import cf-python and cf-plot:
+
+import cfplot as cfp
+
+import cf
+
+#%%
+# 2. Read the field in:
+# Here I've used sample data ggap.nc (and later pressure=850), 
+# but you could use tas_A1.nc (with time=15)
+
+f=cf.read("~/cfplot_data/ggap.nc")[0] 
+
+#%%
+# 3. Create the file with subplots:
+# If you are changing the number of subplots ensure the number of rows * number 
+# of columns = the number of subplots/projections
+# Here we are doing 6 projections so 2x3 is fine
+
+cfp.gopen(rows=2, columns=3, bottom=0.2, file="projections.png")
+
+#%%
+# 4. List the projection types being used:
+# Here we are using Cylindrical/Default, North Pole Stereographic, 
+# South Pole Stereographic, Mollweide, Cropped Lambert Conformal and Robinson
+# However you could also use other such as "rotated", "ortho" or 
+# "merc", "ukcp", "osgb", or "EuroPP"
+# https://ncas-cms.github.io/cf-plot/build/user_guide.html#appendixc
+
+projtypes = ["cyl", "npstere", "spstere", "moll", "lcc", "robin"] 
+
+#%%
+# 5. We then use a for loop to cycle through all the different projection types:
+# Only gpos has 1 added because it can only take 1 as its first value, otherwise there are 
+# errors. There are if statements for some projections (lcc, OSGB and EuroPP) as they have
+# specific requirements for their contour.
+# However, OSGB and EuroPP will require very different data anyway.
+
+for i, proj in enumerate(projtypes):
+    cfp.gpos(i+1) 
+    if projtypes[i] == "lcc":
+        cfp.mapset(proj='lcc', lonmin=-50, lonmax=50, latmin=20, latmax=85)
+    if (projtypes[i]== "OSGB") or (projtypes[i] =="EuroPP"):
+        cfp.mapset(proj=projtypes[i], resolution='50m')
+    else:
+        cfp.mapset(proj=projtypes[i])
+    if i ==len(projtypes)-1:
+         cfp.con(f.subspace(pressure=850), lines=False, title = projtypes[i], colorbar_position=[0.1, 0.1, 0.8, 0.02], colorbar_orientation='horizontal') #to see the marking lines need to be True, but this can be hard to read so if not needed use False
+    else:
+        cfp.con(f.subspace(pressure=850), lines = False, title = projtypes[i], colorbar = False)
+cfp.gclose()