"""Plotting functions used with cartopy."""
import cartopy.crs as ccrs
from cartopy.mpl.geoaxes import GeoAxes
from matplotlib.transforms import offset_copy
from mpl_toolkits.axes_grid1 import AxesGrid
from .text import fmt_lonlat
__all__ = ("GeoAxesGrid", "label_global_map_gridlines")
[docs]
class GeoAxesGrid(AxesGrid):
"""
Grid of cartopy axes.
A subclass of :class:`mpl_toolkits.axes_grid1.AxesGrid` representing
a grid of maps with the same projection :class:`~cartopy.crs.Projection`.
- `axes_class` is defined automatically
- The :class:`AxesGrid` built-in labelling is always switched off,
and instead a standard procedure of creating
grid lines and labels should be used.
"""
[docs]
def __init__(self, fig, rect, nrows_ncols, projection, **axesgrid_kw):
"""
Initialise GeoAxesGrid.
Build a :class:`GeoAxesGrid` instance with a grid nrows*ncols
:class:`GeoAxes` with a projection :class:`~cartopy.crs.Projection`
in :class:`~matplotlib.figure.Figure` *fig* with
*rect=[left, bottom, width, height]* (in
:class:`~matplotlib.figure.Figure` coordinates) or
the subplot position code (e.g., "121").
"""
axesgrid_kw["axes_class"] = (GeoAxes, {"map_projection": projection})
axesgrid_kw["label_mode"] = "" # note the empty label_mode
super().__init__(fig, rect, nrows_ncols, **axesgrid_kw)
[docs]
def label_global_map_gridlines(
fig,
ax,
xticks=None,
yticks=None,
xoff=-10,
yoff=-10,
degree=False,
**text_kw,
):
"""
Label gridlines of a global cartopy map.
Parameters
----------
fig: matplotlib.figure.Figure
Figure object.
ax: cartopy.mpl.geoaxes.GeoAxesSubplot
Cartopy axes.
xticks: array-like, optional
Sequence of longitude ticks.
yticks: array-like, optional
Sequence of latitude ticks.
xoff: float, optional
Longitude label offset from the axis (units are points).
If negative (by default), the labels are drawn at the east boundary,
otherwise at the west boundary.
yoff: float, optional
Latitude label offset from the axis (units are points).
If negative (by default), the labels are drawn at the south boundary,
otherwise at the north boundary.
degree: bool, optional
Add a degree symbol to tick labels.
**text_kw: dict, optional
Label text properties.
"""
# Define what boundary to use
if yticks is None:
yticks = []
if xticks is None:
xticks = []
extent = ax.get_extent(crs=ccrs.PlateCarree())
if xoff <= 0:
xpos = extent[0] # labels at the east boundary
else:
xpos = extent[1] # labels at the west boundary
if yoff <= 0:
ypos = extent[2] # labels at the south boundary
else:
ypos = extent[3] # labels at the north boundary
geodetic_trans = ccrs.Geodetic()
xlab_kw = ylab_kw = {**{"va": "center", "ha": "center"}, **text_kw}
for xtick in xticks:
s = fmt_lonlat(xtick, "lon", degree=degree)
text_transform = offset_copy(
geodetic_trans._as_mpl_transform(ax),
fig=fig,
units="points",
x=0,
y=yoff,
)
ax.text(xtick, ypos, s, transform=text_transform, **xlab_kw)
for ytick in yticks:
s = fmt_lonlat(ytick, "lat", degree=degree)
text_transform = offset_copy(
geodetic_trans._as_mpl_transform(ax),
fig=fig,
units="points",
x=xoff,
y=0,
)
ax.text(xpos, ytick, s, transform=text_transform, **ylab_kw)