point count from in Inverse Distance weighting procedure - QGIS

Question

I have conducted an interpolation using IDW procedure. I have vectorized the interpolation in order to be able to specify a 3 class clasification.

I have additional point dataset indicating the families living in parts of the interpolated area. Each point repsresents a family. I would like to know, how many families live in each area, expressed as the proportion of total families.

How can I achieve this?

Is vectorization of the IDW appropriate here?

Answer 1

I am using ArcGIS. Vectorising the IDW is not necessary straight away, I would follow this method:

1. Run the "Reclass" geoprocessing tool and classify the IDW into the classes you need
2. Convert the reclassed IDW to a polygon using the "Conversion" Tools, I would suggest you don't use the simplify polygons option
3. Name the polygons if you need to and perform a spatial join between the household (family) information and the polygon layer. With the spatial join, set your Polygon as the target and the households as the join. Leave everything else as default.
4. You output will be a new polygon, with the field of interest being "Join_Count", create a new field called "Percentage" or anything that makes sense to you.
5. Run the field calculator on the "Percentage" field, dividing the join count by the total number of households multiplying by 100 to get the percentage. This will give you the percentage of households within that particular polygon.