Clustering adjacent polygons with values over a given threshold with Python

Question

I have a GeoPandas dataframe that looks like the following

    geometry                                            raster_val
0   POLYGON ((1.85626 49.12003, 1.85626 49.11171, ...   28.530001
1   POLYGON ((1.87290 49.12003, 1.87290 49.11171, ...   28.930000
2   POLYGON ((1.88123 49.12003, 1.88123 49.11171, ...   28.670000
3   POLYGON ((1.89788 49.12003, 1.89788 49.11171, ...   28.510000
4   POLYGON ((1.90620 49.12003, 1.90620 49.11171, ...   29.969999

that I can show

f,ax=plt.subplots(figsize=(8,8))
gdf.plot(column='raster_val', scheme='quantiles', legend=True, ax=ax)

I would like to cluster all the adjacent polygons with a given values and create macropolygons based on such aggregration. Let say I want to create macropolygons that have raster_val > 33

Answer 1

You can get macro-polygons by creating bins from the raster value column with pandas cut and then dissolve on the new binned column with geopandas dissolve.

Answer 2

Select polygons where GeoDataFrame's raster values greater than 33

macropolygons  = gdf[gdf['raster_val'] > 33]