fillout

While Matlab FILL, fills inside a polygon, FILLOUT fills outside a boundary. The boundary can be a continuous line, defined by the vectors X,Y or a region defined by the 2-D arrays X,Y.

Syntax:
H = FILLOUT(X,Y,LIM,VARARGIN)

Inputs:
X, Y Boundary vectors (continuous) or 2-D arrays.
LIM Outer limite box, like AXIS, ie, [minX maxX minY maxY], by default the limits of the data is used
VARARGIN Any options of the FILL command. By default the fill color FaceColor) is green and the EdgeColor is none

The screenshot shows the example on the help