Semi-join?

I keep finding things that are trivial in sql are not so in R, so perhaps
you can help me out.

What would be the way in the 'sf' package to retain only polygons from one
coverage that intersect points in another coverage? I think that's a
semi-join.

Roughly: 'select a.* from polys a, points b where st_intersects(a.geom,
b.geom)'

Thanks.

THK

On 5/7/19 8:29 PM, Tim Keitt wrote:

I keep finding things that are trivial in sql are not so in R, so perhaps
you can help me out.

What would be the way in the 'sf' package to retain only polygons from

one

coverage that intersect points in another coverage? I think that's a
semi-join.

Roughly: 'select a.* from polys a, points b where st_intersects(a.geom,
b.geom)'

a[b,]

# or

st_join(a, b, left = FALSE) # no left join gives you inner join

Thanks.

THK

--
Edzer Pebesma
Institute for Geoinformatics
Heisenbergstrasse 2, 48151 Muenster, Germany
Phone: +49 251 8333081

On Tue, May 7, 2019 at 1:39 PM Edzer Pebesma <
edzer.pebesma at uni-muenster.de> wrote:

On 5/7/19 8:29 PM, Tim Keitt wrote:

I keep finding things that are trivial in sql are not so in R, so

perhaps

you can help me out.

What would be the way in the 'sf' package to retain only polygons from

one

coverage that intersect points in another coverage? I think that's a
semi-join.

Roughly: 'select a.* from polys a, points b where st_intersects(a.geom,
b.geom)'

a[b,]

# or

st_join(a, b, left = FALSE) # no left join gives you inner join

Hmm... tried this and for some reasons it was not giving me what I wanted.
I will investigate.

THK

Thanks.

THK

--
Edzer Pebesma
Institute for Geoinformatics
Heisenbergstrasse 2, 48151 Muenster, Germany
Phone: +49 251 8333081

--
Timothy H. Keitt
Professor of Integrative Biology and
Associate Chair for Undergraduate Education
http://www.keittlab.org/