### Name: aRTlayer-getSetMetric
### Title: Set Metrics
### Aliases: getSetMetric,aRTlayer-method getSetMetric union difference xor
###   intersection
### Keywords: connection

### ** Examples

## Not run: 
##D ## difference between two geometries
##D getSetMetric(layer, "difference", ids=c("1", "2"))
##D 
##D ## union of all geometries of the layer
##D getSetMetric(layer, "union", ids=getGeometry(layer)$id)
## End(Not run)



