% Chapter 7: Example 7.22
%            Error function plot and counting of extrema
figure(1);subplot(1,1,1)
h = [1,2,3,4,3,2,1]/15;
M = length(h); n = 0:M-1;
[Hr,w,a,L] = Hr_Type1(h);
subplot(1,2,1);plot(w/pi,Hr);axis([0,1,-0.05,1.1])
xlabel('frequency in pi units');
title('Amplitude Response');hold on
wp = w(1:52); ws = w(197:500);
upb=Hr(1)*ones(length(wp),1);
lpb=(2-Hr(1))*ones(length(wp),1);
ipb=ones(length(wp),1);
plot(wp/pi,upb,'r',wp/pi,ipb,'g',wp/pi,lpb,'r')
usb=Hr(197)*ones(length(ws),1);
lsb=zeros(length(ws),1);
isb=0.5*usb;
plot(ws/pi,usb,'r',ws/pi,isb,'g',ws/pi,lsb,'r');
set(gca,'XTickMode','manual','XTick',[0,0.1,0.39,1])
set(gca,'XTickLabelMode','manual','XTickLabels',[' 0 ';'0.1';'0.4';' 1 '])
set(gca,'XGrid','on')
set(gca,'YTickMode','manual','YTick',[0,0.0394,0.0787,0.933,1,1.067])
set(gca,'YTickLabelMode','manual',...
        'YTickLabels',['-0.04';' 0.0 ';' 0.04';' 0.93';' 1.0 ';' 1.07'])
hold off
%
%Error function plots
subplot(1,2,2); 
erpb=Hr(1:52)-ipb; ersb=Hr(197:500)-isb;
plot(wp/pi,erpb,ws/pi,ersb); axis([0,1,-.55,.55]);
xlabel('frequency in pi units');
title('Error Function');hold on
plot(wp/pi,upb-ipb,'r',wp/pi,lpb-ipb,'r')
plot(ws/pi,usb-isb,'r',ws/pi,lsb-isb,'r');
set(gca,'XTickMode','manual','XTick',[0,0.1,0.39,1])
set(gca,'XTickLabelMode','manual','XTickLabels',[' 0 ';'0.1';'0.4';' 1 '])
set(gca,'XGrid','on')
set(gca,'YTickMode','manual','YTick',[-0.07,0,0.07])
hold off