# misc-gDistance: Distance between geometries In rgeos: Interface to Geometry Engine - Open Source ('GEOS')

 gDistance R Documentation

## Distance between geometries

### Description

Calculates the distance between the given geometries

### Usage

``````gDistance(spgeom1, spgeom2=NULL, byid=FALSE, hausdorff=FALSE, densifyFrac = NULL)
gWithinDistance(spgeom1, spgeom2=NULL, dist, byid=FALSE,
hausdorff=FALSE, densifyFrac=NULL)
``````

### Arguments

 `spgeom1, spgeom2` sp objects as defined in package sp. If spgeom2 is NULL then spgeom1 is compared to itself. `byid` Logical vector determining if the function should be applied across ids (TRUE) or the entire object (FALSE) for spgeom1 and spgeom2 `hausdorff` Logical determining if the discrete Hausdorff distance should be calculated `densifyFrac` Numerical value between 0 and 1 that determines the fraction by which to densify each segment of the geometry. `dist` Numerical value that determines cutoff distance

### Details

Discrete Hausdorff distance is essentially a measure of the similarity or dissimilarity of the two geometries, see references below for more detailed explanations / descriptions.

If `hausdorff` is TRUE and `densifyFrac` is specified then the geometries' segments are densified by splitting each segment into equal length subsegments whose fraction of the total length is equal to `densifyFrac`.

### Value

gDistance by default returns the cartesian minimum distance between the two geometries in the units of the current projection. If `hausdorff` is TRUE then the Hausdorff distance is returned for the two geometries.

gWithinDistance returns TRUE if returned distance is less than or equal to the specified `dist`.

### Author(s)

Roger Bivand & Colin Rundel

### References

`gWithinDistance`

### Examples

``````

p1 = readWKT("POLYGON((0 0,1 0,1 1,0 1,0 0))")
p2 = readWKT("POLYGON((2 0,3 1,4 0,2 0))")

gDistance(pt1,pt2)
gDistance(p1,pt1)
gDistance(p1,pt2)
gDistance(p1,p2)

p3 = readWKT("POLYGON((0 0,2 0,2 2,0 2,0 0))")
p4 = readWKT("POLYGON((0 0,2 0,2 1.9,1.9 2,0 2,0 0))")
p5 = readWKT("POLYGON((0 0,2 0,2 1.5,1.5 2,0 2,0 0))")
p6 = readWKT("POLYGON((0 0,2 0,2 1,1 2,0 2,0 0))")
p7 = readWKT("POLYGON((0 0,2 0,0 2,0 0))")

gDistance(p3,hausdorff=TRUE)
gDistance(p3,p4,hausdorff=TRUE)
gDistance(p3,p5,hausdorff=TRUE)
gDistance(p3,p6,hausdorff=TRUE)
gDistance(p3,p7,hausdorff=TRUE)
``````

rgeos documentation built on July 26, 2023, 5:42 p.m.