How to count points in polygons with R?

I’m quite new to R and especially GIS with R. So recently I had to proceed to a quite simple analysis: counting health centers (points) per administrative unit (polygons).

How to create spatial polygons from a Dataframe?

I have a dataframe containing the coordinates of a set of polygons. This is how I would convert it to a spatialPolygons (package sp)

Which is an example of a simple feature geometry?

Low-level examples are: Just to make the point, we can for instance rotate the counties of North Carolina 90 degrees clockwise around their centroid, and shrink them to 75% of their original size: The coordinate reference system of objects of class sf or sfc is obtained by st_crs, and replaced by st_crs<-:

How to convert a line to a polygon?

For converting lines to polygons, see also st_polygonize below. convert from XX to MULTIXX, e.g. LINESTRING to MULTILINESTRING convert from MULTIXX to XX if MULTIXX has length one (else, it will still convert but warn about loss of information)

How to identify polygon containing point with are SF?

FYI those coordinates are locations of weather stations, I used this approach to identify weather stations located in major cities in Australia. To find the countries of a data.frame with lat-long coordinates, convert them to an sf object with sf::st_as_sf (mydf, coords=c (“lon”,”lat”), crs=4326).

How to intersect points and polygons in are stack?

Note that these ‘valid’ functions depend on a sf installation compiled with liblwgeom. You do this in one line with point.in.poly fom spatialEco package. from the documentation: point.in.poly “intersects point and polygon feature classes and adds polygon attributes to points”.

Which is used to handle spatial objects in rgeos?

So, you can just use gContains () in the rgeos package and colSums (). You can achieve the same using the sf package. Check the reproducible and commented code below. The package sf is used to handle spatial objects as simple features objects.

How to calculate the number of points in a polygon?

Given a set of points, and a set of polygons, computes the number of points in each polygon. A SpatialPoints or SpatialPointsDataFrame object. A SpatialPolygons or SpatialPolygonsDataFrame object. A list of integers of the same length as the number of polygons in polys, giving the number of points from pts .

How to write gcontains function in rgeos?

If you’d look into the function, you’d realize that the function is written as colSums (gContains (polys, pts, byid = TRUE)). So, you can just use gContains () in the rgeos package and colSums ().

How to determine the interior of a polygon?

The following C function returns INSIDE or OUTSIDE indicating the status of a point P with respect to a polygon with N points. The following code is by Randolph Franklin, it returns 1 for interior points and 0 for exterior points.

How to count the number of point features within a polygon?

Go to ArcToolbox > Analysis Tools > Overlay > Spatial Join. Join Operation: JOIN_ONE_TO_ONE and check the Keep All Target Features option. Match Option: COMPLETELY_CONTAINS. For this option, the point features in the join features are matched when a polygon target feature completely contains them.

How to count points in polygons with R?