$$SHAPE_{SD} = sd(SHAPE[patch_{ij}])$$
where \(SHAPE[patch_{ij}]\) is the shape index of each patch.
SHAPE_SD is a 'Shape metric'. Each class is summarised as the standard deviation
of each patch belonging to class i. SHAPE describes the ratio between the actual perimeter of
the patch and the square root of patch area.
Because the metric is based on distances or areas please make sure your data
is valid using check_landscape.
Behaviour
Equals SHAPE_SD = 0 if all patches have an identical shape index.
Increases, without limit, as the variation of the shape index increases.