[R-sig-Geo] Dealing with non-nested geographic units using the RQGIS and tigris R packages

[Richard]

I recently came across this tutorial suggesting that the RQGIS and tigris R
packages could be used to overcome issues with non-nested geographies:

https://rpubs.com/corey_sparks/256942

I'm trying to apply this to some data I have where I would like to look at
Census Block Groups nested within Zip Code Tabulation Areas. Specifically,
I'd like to compute a segregation index using Census Block Groups as the
lower units and Zip Code Tabulation Areas as the higher level units.

I am confused about how these R packages deal with this issue of non-nested
units. Here's the explanation from the tutorial:

"In order to get around this problem [non-nested units], we can use the
QGIS application to perform a geographic intersection between two spatial
polygon layers that we want to use. This will allow us to merge the
population data at the census tract level to a higher level, so we can
calculate a segregation index."

Can anyone say more about how this is possible? I can run the code in the
tutorial but I don't understand what it's doing.

Thanks!

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