interpln - linear interpolation
given xyd a set of points in the xy-plane which increasing abscissae and x a set of abscissae, this function computes y the corresponding y-axis values by linear interpolation.
x=[1 10 20 30 40]; y=[1 30 -10 20 40]; plot2d(x',y',[-3],"011"," ",[-10,-40,50,50]); yi=interpln([x;y],-4:45); plot2d((-4:45)',yi',[3],"000");