graphics_toolkit gnuplot

% "color" is temporary, because of gnuplot bug (see below)
hfig = figure("color", .85*[1 1 1], "position", [100 100 488 512]);
set(gca, "color", .85*[1 1 1])

xmax = 3000;

% subplot() undoes the "color" attempts above.  (gnuplot bug)
subplot(6,1,1)
L = 100;
f = ones(1,L)/L;
plot(-100:200-1, [zeros(1,100) f*L zeros(1,100)], "linewidth", 2, "color", "magenta")
set(gca, "color", "white")
title("Circular convolution example", "FontSize",12)
text(100, 1.6, "h[n]")
text(xmax/2, 0.4, '\leftarrow n \rightarrow')
ylim([0 2])
xlim([-100 xmax])
set(gca,"XTick",[]); set(gca,"YTick",[])

subplot(6,1,2)
a = [zeros(1,20) ones(1,L) zeros(1,300) 0.5*ones(1,100) zeros(1,1000-L-20-400)];
b = [zeros(1,1000-L-20) ones(1,L) zeros(1,20)];
a1 = [zeros(1,1000) a zeros(1,1000)];
b1 = [zeros(1,1000) b zeros(1,1000)];
plot(1:length(a1), a1, "color", "blue", 1:length(a1), b1, "color", "red")
set(gca, "color", "white")
text(200, 1.6, "X[n]")
ylim([0 2])
xlim([0 xmax])
set(gca,"XTick",[]); set(gca,"YTick",[])

subplot(6,1,3)
a1 = conv(a1,f);
b1 = conv(b1,f);
plot(1:length(a1), a1+b1, "color", "green", "linewidth", 2)
set(gca, "color", "white")
text(200, 1.6, "X[n] * h[n]")
ylim([0 2*max(a1)])
xlim([0 xmax])
set(gca,"XTick",[]); set(gca,"YTick",[])

subplot(6,1,4)
a = [a a a];
b = [b b b];
L = 1:length(a);
plot(L, a, "color","blue", L, b, "color","red")
set(gca, "color", "white")
text(200, 2.0, 'X_N[n]')
ylim([0 2.5])
xlim([0 xmax])
set(gca,"XTick", [1000 2000])
set(gca,"XTickLabel",["N"; "2N"])
set(gca,"YTick",[])

subplot(6,1,5)
a1 = conv(a,f);
b1 = conv(b,f);
b1(1:90) = b1(3000+[1:90]);
L = 1:length(a1);
plot(L,a1,"color","blue", L,b1, "color","red")
set(gca, "color", "white")
text(200, 1.6, 'components of X_N[n] * h[n]')
ylim([0 2*max(a1)])
xlim([0 xmax])
set(gca,"XTick",[]); set(gca,"YTick",[])

subplot(6,1,6)
c = a1+b1;
L = length(c);
k=1100;
plot(1:k, c(1:k), "color","red", k+(1:900), c(k+(1:900)), "color", "green", "linewidth", 2, (k+900+1):xmax, c((k+900+1):xmax), "color","red")
set(gca, "color", "white")
text(200, 1.6, 'X_N[n] * h[n]')
ylim([0 2*max(a1+b1)])
xlim([0 xmax])
set(gca,"XTick",[]); set(gca,"YTick",[])

text(1163, -1, "X[n] * h[n]", "fontsize", 16)
annotation("line", [.414 .414], [.136 .045])
annotation("line", [.647 .647], [.136 .045])

% I prefer the version created by the export function on the GNUPlot figure,
% because the dimensions are better.
print(hfig,"-dpng","-color", 'C:\Users\BobK\Circular convolution example.png')