Pass norm kwarg to PolyCollection

[andrewdnolan]

Closes #44, which was introduced by #29. norm must be passed to the Polycollection instantiation.

CC'ing @cbegeman, as this should fix the issues you've seen with mosaic 1.12.0 in polaris.

[andrewdnolan]

Testing:

Using the same MWE example code the from the issue documentaiton #44:

import cartopy.crs as ccrs
import matplotlib.colors as cols
import matplotlib.pyplot as plt
import mosaic
import xarray as xr

from pathlib import Path

transform = ccrs.PlateCarree()
projection = ccrs.PlateCarree()

ds = mosaic.datasets.open_dataset("QU.240km")

descriptor = mosaic.Descriptor(ds, projection, transform)

nCells = ds.sizes["nCells"]
vmin = nCells // 2 - nCells // 10
vmax = nCells // 2 + nCells // 10

norm = cols.Normalize(vmin=vmin, vmax=vmax)

def plot(ds, descriptor, kwargs):
    fig, ax = plt.subplots(
        constrained_layout=True, subplot_kw={"projection": projection}
    )

    pc = mosaic.polypcolor(
        ax, descriptor, ds.indexToCellID, **kwargs
    )

    fig.colorbar(pc, extend='both', shrink=0.6)
    
    plt.show()

Specifying vmin/vmax explicitly

plot(ds, descriptor, {"vmin": vmin, "vmax": vmax})

Passing vmin/vmax to norm, and then providing mosaic with norm argument

plot(ds, descriptor, {"norm": norm})

[cbegeman]

@andrewdnolan Great, thanks! It looks like you've done adequate testing here so I'll wait for the mosaic update in Polaris unless you'd like me to try this fix out.

[andrewdnolan]

I've also tested with the 240km output from the spherical rotation_2d polaris testcase. The issue also appears to be fixed there.

I'll get this merged and have a patch release out ASAP.