jitter geometries

`st_jitter(x, amount, factor = 0.002)`

- x
object of class

`sf`

or`sfc`

- amount
numeric; amount of jittering applied; if missing, the amount is set to factor * the bounding box diagonal; units of coordinates.

- factor
numeric; fractional amount of jittering to be applied

jitters coordinates with an amount such that `runif(1, -amount, amount)`

is added to the coordinates. x- and y-coordinates are jittered independently but all coordinates of a single geometry are jittered with the same amount, meaning that the geometry shape does not change. For longlat data, a latitude correction is made such that jittering in East and North directions are identical in distance in the center of the bounding box of `x`

.

```
nc = read_sf(system.file("gpkg/nc.gpkg", package="sf"))
pts = st_centroid(st_geometry(nc))
plot(pts)
plot(st_jitter(pts, .05), add = TRUE, col = 'red')
plot(st_geometry(nc))
plot(st_jitter(st_geometry(nc), factor = .01), add = TRUE, col = '#ff8888')
```