Calculating what proportion of polygons is covered by rivers

Juta,
I think you can do something along these lines:

library(raster)
library(rgeos)

x <- union(districts, rivers)
a <- gArea(x, byid=TRUE)
head(x)
head(a)

or
x <- intersect(districts, rivers)

and compare to 'districts'

Robert


On Sun, Nov 30, 2014 at 2:59 PM, Juta Kawalerowicz
<juta.kawalerowicz at nuffield.ox.ac.uk> wrote:

Hi, I have question - I am looking for ideas how to proceed.

I have a SpatialPolygonsDataFrame with polygons (300) representing
districts. Another SpatialPolygonsDataFrame has 700 polygons and these
polygons represent rivers and flooding areas. My question is how would

you

go about calculating what proportion of districts is covered by rivers

and

flooding areas?

My first intuition was to rasterize it and then use the extract function
but maybe I am overcomplicating this. Any ideas would be appreciated.

Thanks,
Juta

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