Unable to color polygons based on their attributes

Q&A
1

Hi everyone,
I am facing issue while trying to color polygons based on their attributes.
I tried to do this through this method (https://flint.soest.hawaii.edu/t/how-to-color-polygons-of-a-geopandas-dataframe-in-pygmt/1138), but it still not solved.

I am trying to color the polygons based on the column ‘Year_only’ (in shapefile). In case anyone would like to see it: Upload Files | Free File Upload and Transfer Up To 10 GB (here is the shapefile that I used; it a small file).

Here are the codes I used:

fig = pygmt.Figure()
pygmt.makecpt(cmap="vik", series=[2017, 2021, 1], continuous=True, reverse=True)
fig.plot(data=footprint_each_DEMs,
         cmap=True, 
         color="+z", 
         close=True, 
         aspatial="Z=Year",
         pen="thinnest,red,-"
        )
fig.colorbar(position="jMR+jMR+w8c+o0.1c/1c+e")
fig.show()

I followed the same method as in the example (https://flint.soest.hawaii.edu/t/how-to-color-polygons-of-a-geopandas-dataframe-in-pygmt/1138), but It seems not able to get what I expect.

What I got is attached below. The polygons are not colored based on the attributes, though the right colorbar appears.

footprints
footprints1858×1698 55.2 KB

But I expect something like below, with Years as colorbar.

index

It would be great if anyone can give me some hint to get so.

Thank you.
Arindan

2

should it not be Year_only then?

3

Hi Mikhail,
Thanks for seeing this.
Even if I use aspatial="Z=Year", It doesn’t appear what I expected. aspatial="Z=Year" it has also the date attributes.

Or I think there is some other issue or I am doing some mistake.

4

you should try aspatial="Z=Year_only"

5

Hi Mikhail,

Thanks.
aspatial="Z=Year_only" did not work. It gives the same plot with red outlines, as shown in my first comment.

Is it something like the issue with the pen color?

Arindan

6 
import pygmt
filename = 'footprint/footprint_each_DEMs.shp'

fig = pygmt.Figure()
pygmt.makecpt(cmap="vik", series=[2017, 2021, 1], continuous=True, reverse=True)
fig.plot(data=filename,
         cmap=True, 
         color='+z', 
         close=True, 
         aspatial='Z=Year_only',
         pen="thinnest,red,-"
        )
fig.colorbar(position="jMR+jMR+w8c+o0.1c/1c+e")
fig.show()

test
test1858×1698 91.5 KB

1 Like
7

Hi Mikhail,

Thanks for this. I was looking for this.
What was the mistake in my code is: I was using geopandas to open the shapefile.
Like: footprint_each_DEMs = gpd.read_file(topdir + '/Footprint of dh/footprint_each_DEMs.shp')

Thanks for giving it a try and the solution.

Best, Arindan

8

I actually have no idea how to do it using geopandas

I would be glad to learn if somebody who knows could explain it to us.