This is obviously useful, especially for larger grids.
Althought not every 2D grid is triangular, it can be easily triangulated (which is done for a number of plotting methods, since matplotlib can will only draw contours for triangles e.g.).
The following suffices for Ugrid2d topologies in the _PlotMethods accessor:
def to_holoviews(self):
import holoviews
import pandas as pd
grid = self.grid
da = self.darray
(_, _, triangles), index = grid.triangulation
name = getattr(da, "name", "data")
vertices = pd.DataFrame(
data=grid.node_coordinates,
columns=("x", "y"),
)
triangles = pd.DataFrame(
data=triangles,
columns=("v0", "v1", "v2"),
)
dim = get_ugrid_dim(grid, da)
if dim == NODE:
vertices[name] = da
elif dim == FACE:
triangles[name] = da.isel({grid.face_dimension: index})
else:
raise ValueError("only supports data on nodes or faces")
return holoviews.TriMesh((triangles, vertices))
Then, to draw something:
import holoviews as hv
from datashader import rasterize
hv.extension("matplotlib")
rasterize(uda.to_holoviews()).opts(colorbar=True)
The datashader/holoviews isn't entirely obvious to me. Should we add (more) methods to let it resemble the "standard" plotting arguments (i.e. like xarray/matplotlib?)
Should we default to bokeh/matplotlib as the extension? Not setting it results in nothing being shown.
Having to call rasterize yourself is a bit annoying. Something like .ugrid.holoviews.plot() could be an option but:
We're stacking a lot of accessors...
There are arguments for both the rasterize function as well as the plotting options. Should they be combined?
Secondly, there's a package called hvplot: https://hvplot.holoviz.org/
It adds an hvplot and interactive accessor to dataframes and xarray objects. This seems like it's more work, because it actually does data selection.
Holoviews and Datashader supports TriMesh/trimesh (resp.): https://datashader.org/user_guide/Trimesh.html
This is obviously useful, especially for larger grids.
Althought not every 2D grid is triangular, it can be easily triangulated (which is done for a number of plotting methods, since matplotlib can will only draw contours for triangles e.g.).
The following suffices for Ugrid2d topologies in the _PlotMethods accessor:
Then, to draw something:
What makes it not totally trivial:
Having to call rasterize yourself is a bit annoying. Something like
.ugrid.holoviews.plot()could be an option but:Secondly, there's a package called
hvplot: https://hvplot.holoviz.org/ It adds anhvplotandinteractiveaccessor to dataframes and xarray objects. This seems like it's more work, because it actually does data selection.