[R-sig-Geo] How to filter a spatial object in sf

[Matt Lewis]

Dear Manuel,

st_filter by default takes .predicate = st_intersects. The 3 polygons 
you filter to are adjacent to five others, so st_filter returns the 3 
you want and the 5 others which touch too. To avoid this behaviour you 
can specify the .predicate argument to another option like st_within as 
in:

nc_filter <- st_filter(nc, nc_smaller, .predicate = st_within)

Hope this helps.

All the best,

Matt

On 2021-06-30 16:52, Manuel Spínola wrote:

> I would like to retain the information stored in a larger spatial 
> object
> for a subset of features from a smaller spatial object.  I tried a
> st_filter but I cannot achieve my goal.
> 
> nc = st_read(system.file("shape/nc.shp", package="sf"))
> 
> nc_smaller <- nc %>% filter(CNTY_ID %in% c(1825, 1827, 1828))
> 
> nc_filter <- st_filter(nc, nc_smaller)
> 
> The nc_smaller has 3 features, but the nc_filter ended with 8 features. 
>  I
> was expecting to have on 3 features in the nc_filter.
> 
> Manuel
> 
> --
> *Manuel Spínola, Ph.D.*
> Instituto Internacional en Conservación y Manejo de Vida Silvestre
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