function [xx,yy] = stepfcn(c,v,xmin,xmax)
%
% Create data for plotting a step function with   plot(xx,yy)
%
% Assume xmin < v1 < ... < vN-1 < xmax
%
xx = [ xmin kron(v,[1 1]) xmax ];
yy = kron(c,[1 1]);
