I need to make a heat map with the number of cases by neighborhood.
- a polygon shapefile with the neighborhoods, and
- a CSV file containing the name of the neighborhood and the number of cases.
Is there a way to do this in QGIS 3.4 LTS?
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"Heatmap" makes me assume a point density visualisation. What you have is aggregated polygon data it would seem. So you would need to generate the points after first joining the CSV case number column to the polygons via a common ID.
You could then turn that into a heatmap either by using "Generate random points in polygons" in the Processing toolbox based on the case count, and then turning that into a heatmap (just use heatmap as symbology for the points).
Or you could generate centroid points for each neighbourhood and visualise those as a heatmap by weighting each point based on the number of cases (again with point heatmap symbology and use the weighting field).
However, I think this would be methodologically dubious as the heatmap would be influenced by the shape of the areas that the points are generated from. So I would rather recommend visualising this as a choropleth map instead to get a more accurate representation of the data.