%
%  w02steep.m -- djm -- 18 jan 06
%    - steepest descent contours
%
% - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 

aa = -0.5;

dx = pi/128;  x = -pi/2:dx:+3*pi/2;
dy = pi/128;  y =   0:dy:+0.75*pi;

[xx,yy] = meshgrid(x,y);

zz = xx + i*yy;

ff = cos(zz);

figure(7);  clf;  hold on
contourf(x,y,real(i*(zz-aa*ff)),30,'w');  colorbar('vert')
caxis([-2 0]);  colorbar('vert')

ph = [0 pi/2 pi];
[c1,c2] = contour(x,y,imag(i*(zz-aa*ff)),[ph-aa*cos(ph)],'k');  
set(c2,'linewidth',2)

axis([min(x) max(x) 0 max(y)])

title(['\bf steepest descent analysis'],'fontsize',14)
xlabel('\bf real axis','fontsize',12)
ylabel('\bf imag axis','fontsize',12)