draw a regular polygon
xrpoly(orig,n,r,[theta])
:orig vector of size 2. : :n integer, number of sides. : :r real scalar. : :theta real, angle in radian; 0 is the default value. :
xrpoly draws a regular polygon with n sides contained in the circle of diameter r and with the origin of the circle set at point orig. theta specifies a rotation angle in radian. This function uses the current graphics scales.
`plot2d`_(0,0,-1,"012"," ",[0,0,10,10])
xrpoly([5,5],5,5)