poly2pwl

POLY2PWL  Converts polynomial cost variable to piecewise linear.
   PWLCOST = POLY2PWL(POLYCOST, PMIN, PMAX, NPTS) converts the polynomial
   cost variable POLYCOST into a piece-wise linear cost by evaluating at
   NPTS evenly spaced points between PMIN and PMAX. If the range does not
   include 0, then it is evaluated at 0 and NPTS-1 evenly spaced points
   between PMIN and PMAX.

0001 function pwlcost = poly2pwl(polycost, Pmin, Pmax, npts)
0002 %POLY2PWL  Converts polynomial cost variable to piecewise linear.
0003 %   PWLCOST = POLY2PWL(POLYCOST, PMIN, PMAX, NPTS) converts the polynomial
0004 %   cost variable POLYCOST into a piece-wise linear cost by evaluating at
0005 %   NPTS evenly spaced points between PMIN and PMAX. If the range does not
0006 %   include 0, then it is evaluated at 0 and NPTS-1 evenly spaced points
0007 %   between PMIN and PMAX.
0008 
0009 %   MATPOWER
0010 %   Copyright (c) 1996-2016, Power Systems Engineering Research Center (PSERC)
0011 %   by Ray Zimmerman, PSERC Cornell
0012 %
0013 %   This file is part of MATPOWER.
0014 %   Covered by the 3-clause BSD License (see LICENSE file for details).
0015 %   See http://www.pserc.cornell.edu/matpower/ for more info.
0016 
0017 [PW_LINEAR, POLYNOMIAL, MODEL, STARTUP, SHUTDOWN, NCOST, COST] = idx_cost;
0018 
0019 pwlcost = polycost;
0020 [m, n] = size(polycost);            %% size of piece being changed
0021 pwlcost(:, MODEL)  = PW_LINEAR;     %% change cost model
0022 pwlcost(:, COST:n) = 0;             %% zero out old data
0023 pwlcost(:, NCOST)  = npts;          %% change number of data points
0024 pwlcost(1, COST+2*(npts-1)+1) = 0;  %% expand as needed
0025 
0026 for i = 1:m
0027     if Pmin(i) > 0
0028         step = (Pmax(i) - Pmin(i)) / (npts - 2);
0029         xx = [0 Pmin(i):step:Pmax(i)];
0030     elseif Pmax(i) < 0
0031         step = (Pmax(i) - Pmin(i)) / (npts - 2);
0032         xx = [Pmin(i):step:Pmax(i) 0];
0033     else
0034         step = (Pmax(i) - Pmin(i)) / (npts - 1);
0035         xx = (Pmin(i):step:Pmax(i));
0036     end
0037     yy = totcost(polycost(i, :), xx);
0038     pwlcost(i,      COST:2:(COST + 2*(npts-1)    )) = xx;
0039     pwlcost(i,  (COST+1):2:(COST + 2*(npts-1) + 1)) = yy;
0040 end