[w,b]=sqmp(m,r1,r2,nr,t1,t2,nt)

function [w,b]=sqmp(m,r1,r2,nr,t1,t2,nt)
%
% [w,b]=sqmp(m,r1,r2,nr,t1,t2,nt)
% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% This function evaluates the conformal 
% mapping produced by the Schwarz-Christoffel 
% transformation w(z) mapping abs(z)<=1 inside
% a square having a side length of two.  The 
% transformation is approximated in series form 
% which converges very slowly near the corners.
% This function is the same as squarmap of
% chapter 2 with no plotting.
%
% m        - number of series terms used
% r1,r2,nr - abs(z) varies from r1 to r2 in 
%            nr steps
% t1,t2,nt - arg(z) varies from t1 to t2 in 
%            nt steps (t1 and t2 are 
%            measured in degrees)
% w        - points approximating the square
% b        - coefficients in the truncated 
%            series expansion which has 
%            the form
%
%            w(z)=sum({j=1:m},b(j)*z*(4*j-3))
%
%----------------------------------------------

% Generate polar coordinate grid points for the 
% map. Function linspace generates vectors with 
% equally spaced components.
r=linspace(r1,r2,nr)'; 
t=pi/180*linspace(t1,t2,nt);
z=(r*ones(1,nt)).*(ones(nr,1)*exp(i*t));

% Compute the series coefficients and evaluate 
% the series
k=1:m-1; 
b=cumprod([1,-(k-.75).*(k-.5)./(k.*(k+.25))]);
b=b/sum(b); w=z.*polyval(b(m:-1:1),z.^4);