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I'm trying to understand how the kdims work for Polygon plots in geoviews. There is a similar question here but it hasn't really been answered - GeoViews: add a slider to chloropleth with Polygon geometries

In http://geo.holoviews.org/user_guide/Geometries.html the line 

gv.Polygons(world, vdims='pop_est')

yields a world map with polygons shaded by population, and I think what it's somehow doing is getting lat/long as the kdims but I don't understand how this works. If I try to specify 'geometry' as the kdims I get an error "Expected two kdims to use GeoDataFrame, found 1."

My end goal is to be able specify the kdims so that I can also specify a "year" parameter as the kdims and get a scrollbar on the map.

piedpiper
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1 Answers1

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I think you are looking for something like (see also here: https://nbviewer.jupyter.org/github/poplarShift/pyviz-recipes/blob/master/notebooks/data_formats.ipynb)

import geoviews as gv
import geopandas as gpd
world = gpd.read_file(gpd.datasets.get_path('naturalearth_lowres'))
import holoviews as hv
hv.extension('bokeh')

hv.Dataset(world, kdims=['Longitude', 'Latitude', 'continent'], vdims='pop_est').to(gv.Polygons)
doppler
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  • Thank you for your comment. When I try your code I still get a Data Error - "Expected two kdims to use GeoDataFrame, found 3". Did the code work for you? – piedpiper Apr 20 '19 at 17:39
  • Yes. I'm on: geoviews version: 1.6.2 holoviews version: 1.12.1 geopandas version: 0.4.1 bokeh version: 1.1.0 but I'm not sure if recent updates have impacted this much – doppler Apr 21 '19 at 15:30
  • @doppler thanks for your oneliner this seems to drastically simplify the use of GeoViews, however I can't seem to get around the `ValueError: All value dimensions on a Contours element must be scalar` – Tom Hemmes Aug 12 '19 at 14:31
  • That is pretty weird given my code does not even directly call `Contours`. If that is the error you get when executing the code given in my answer, you may want to check your versions are recent, and consider filing a bug report. – doppler Aug 16 '19 at 17:03