POLYGON command

Syntax: | `POLYGON xpoly ypoly xdata ydata key`
Qualifiers: | `\INSIDE, \OUTSIDE`
Defaults: | `\INSIDE`

The `POLYGON` command creates a vector, `key`, which will have the same length as the input vectors, `xdata` and `ydata`. By default, `key[i] = 1` if the point `(xdata[i],ydata[i])` is inside the polygon defined by input vectors `xpoly` and `ypoly`, otherwise `key[i] = 0`. If the `\OUTSIDE` qualifier is used, `key[i] = 0` if the point `(xdata[i],ydata[i])` is inside the polygon, otherwise `key[i] = 1`.

Example

     GENERATE\RANDOM X -5 5 2000       ! generate some "data"
     GENERATE\RANDOM Y 10 20 2000      !
     WINDOW 5                          !
     SET PLOTSYMBOL -11                ! choose unjoined point plotting symbol
     GRAPH X Y                         ! display the data graphically
     XP = {-0.5;1.2;-0.2;1.3;-3;-2}    ! the polygon vertices
     YP = {13;13.5;16;18.5;18;14}      !
     POLYGON\OUTSIDE XP YP X Y K       !! find data points outside polygon, create key vector, K
     WINDOW 7                          !
     SET PLOTSYMBOL -11                ! choose unjoined point plotting symbol
     IDX = WHERE(K=1)                  ! choose indices of points outside polygon
     GRAPH X[IDX] Y[IDX]               ! display data without unwanted points
     SET PLOTSYMBOL 0                  ! choose no plotting symbol
     GRAPH\OVERLAY XP//{-0.5} YP//{13} ! overlay the polygon (close by appending first point)