# coding=utf-8
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import numpy as np
# guarded imports
try:
import matplotlib.pyplot as plt
except ImportError:
plt = None
try:
import cartopy
import cartopy.crs as ccrs
except ImportError:
cartopy = None
ccrs = None
def _check_plotting_dependencies():
if plt is None:
raise ImportError("matplotlib is required for plotting functions. Install it with 'pip install matplotlib'")
if cartopy is None:
raise ImportError("cartopy is required for map plotting. Install it with 'pip install cartopy'")
def get_projection(
projection,
central_latitude=0,
central_longitude=0,
):
"""
Get a cartopy projection object for map plotting.
Parameters
----------
projection : str
Projection type ("orthographic", "robinson", "platecarree", "mollweide")
central_latitude : float, optional
Central latitude for the projection, by default 0
central_longitude : float, optional
Central longitude for the projection, by default 0
Returns
-------
cartopy.crs.Projection
Cartopy projection object
Raises
------
ValueError
If projection type is not supported
"""
if projection == "orthographic":
proj = ccrs.Orthographic(central_latitude=central_latitude, central_longitude=central_longitude)
elif projection == "robinson":
proj = ccrs.Robinson(central_longitude=central_longitude)
elif projection == "platecarree":
proj = ccrs.PlateCarree(central_longitude=central_longitude)
elif projection == "mollweide":
proj = ccrs.Mollweide(central_longitude=central_longitude)
else:
raise ValueError(f"Unknown projection mode {projection}")
return proj
[docs]
def plot_sphere(
data,
fig=None,
projection="robinson",
cmap="RdBu",
title=None,
colorbar=False,
coastlines=False,
gridlines=False,
central_latitude=0,
central_longitude=0,
lon=None,
lat=None,
**kwargs,
):
"""
Plots a function defined on the sphere using pcolormesh
Parameters
----------
data : numpy.ndarray or torch.Tensor
Data to plot with shape (nlat, nlon)
fig : matplotlib.figure.Figure, optional
Figure to plot on, by default None (creates new figure)
projection : str, optional
Map projection type, by default "robinson"
cmap : str, optional
Colormap name, by default "RdBu"
title : str, optional
Plot title, by default None
colorbar : bool, optional
Whether to add a colorbar, by default False
coastlines : bool, optional
Whether to add coastlines, by default False
gridlines : bool, optional
Whether to add gridlines, by default False
central_latitude : float, optional
Central latitude for projection, by default 0
central_longitude : float, optional
Central longitude for projection, by default 0
lon : numpy.ndarray, optional
Longitude coordinates, by default None (auto-generated)
lat : numpy.ndarray, optional
Latitude coordinates, by default None (auto-generated)
**kwargs
Additional arguments passed to pcolormesh
Returns
-------
matplotlib.collections.QuadMesh
The plotted image object
"""
# make sure cartopy exist
_check_plotting_dependencies()
if fig is None:
fig = plt.figure()
nlat = data.shape[-2]
nlon = data.shape[-1]
if lon is None:
lon = np.linspace(0, 2 * np.pi, nlon + 1)[:-1]
if lat is None:
lat = np.linspace(np.pi / 2.0, -np.pi / 2.0, nlat)
Lon, Lat = np.meshgrid(lon, lat)
# convert radians to degrees
Lon = Lon * 180 / np.pi
Lat = Lat * 180 / np.pi
# get the projection. Latitude is shifted to match plot_sphere
proj = get_projection(projection, central_latitude=central_latitude, central_longitude=central_longitude)
ax = fig.add_subplot(projection=proj)
# contour data over the map.
im = ax.pcolormesh(Lon, Lat, data, cmap=cmap, transform=ccrs.PlateCarree(), antialiased=False, **kwargs)
# add features if requested
if coastlines:
ax.add_feature(cartopy.feature.COASTLINE, edgecolor="white", facecolor="none", linewidth=1.5)
# add colorbar if requested
if colorbar:
plt.colorbar(im)
# add gridlines
if gridlines:
ax.gridlines(crs=ccrs.PlateCarree(), draw_labels=False, linewidth=1, color="gray", alpha=0.6, linestyle="--")
# add title with smaller font
plt.title(title, y=1.05, fontsize=8)
return im
[docs]
def imshow_sphere(data, fig=None, projection="robinson", title=None, central_latitude=0, central_longitude=0, **kwargs):
"""
Displays an image on the sphere
Parameters
----------
data : numpy.ndarray or torch.Tensor
Data to display with shape (nlat, nlon)
fig : matplotlib.figure.Figure, optional
Figure to plot on, by default None (creates new figure)
projection : str, optional
Map projection type, by default "robinson"
title : str, optional
Plot title, by default None
central_latitude : float, optional
Central latitude for projection, by default 0
central_longitude : float, optional
Central longitude for projection, by default 0
**kwargs
Additional arguments passed to imshow
Returns
-------
matplotlib.image.AxesImage
The displayed image object
"""
# make sure cartopy exist
_check_plotting_dependencies()
if fig is None:
fig = plt.figure()
# get the projection. Latitude is shifted to match plot_sphere
proj = get_projection(projection, central_latitude=central_latitude, central_longitude=central_longitude + 180)
ax = fig.add_subplot(projection=proj)
# contour data over the map.
im = ax.imshow(data, transform=ccrs.PlateCarree(), **kwargs)
# add title
plt.title(title, y=1.05)
return im
