Matlab graph not showing

clear;
close all;
s1=0.535*exp(1i*2*pi/3); s2=0.535*exp(1i*pi); s3=0.535*exp(1i*4*pi/3);
a1=-0.268-0.154*1i; a2=0.535; a3=-0.268+0.154*1i;
w=linspace(0,pi,200);
H1=a1./(2*((1-exp(-1i*w))/(1+exp(-1i*w)))-s1);
H2=a2./(2*((1-exp(-1i*w))/(1+exp(-1i*w)))-s2);
H3=a3./(2*((1-exp(-1i*w))/(1+exp(-1i*w)))-s3);
H=H1+H2+H3;
subplot(1,2,1);
plot(w/pi,abs(H));
ylabel('abs(H)');
xlabel('w/pi (rad/cycle)');
subplot(1,2,2);
plot(w/pi,20*log10(abs(H)));
ylabel('dB');
xlabel('w/pi (rad/cycle)');

My graph above gives me 2 blank graphs when I run the code and I don't know why, can anyone that is more experienced with matlab tell me why? Thanks in advance

[Sander Grosemans]

I found it has to do that H is just a value, while it is supposed to be a double. But I still don't know how to fix it

Answer 1

[Star Strider]

Use element-wise division (./) instead of (/) and it works —

s1=0.535*exp(1i*2*pi/3); s2=0.535*exp(1i*pi); s3=0.535*exp(1i*4*pi/3);
a1=-0.268-0.154*1i; a2=0.535; a3=-0.268+0.154*1i;
w=linspace(0,pi,200);
H1=a1./(2*((1-exp(-1i*w))./(1+exp(-1i*w)))-s1);
H2=a2./(2*((1-exp(-1i*w))./(1+exp(-1i*w)))-s2);
H3=a3./(2*((1-exp(-1i*w))./(1+exp(-1i*w)))-s3);
H=H1+H2+H3;
subplot(1,2,1);
plot(w/pi,abs(H));
ylabel('abs(H)');
xlabel('w/pi (rad/cycle)');
subplot(1,2,2);
plot(w/pi,20*log10(abs(H)));
ylabel('dB');
xlabel('w/pi (rad/cycle)');

See the documentation on Array vs. Matrix Operations for an extended discussion. .

[Sander Grosemans]

Thank you so much it works! Wishing you and your family a good health in these difficult times

[Star Strider]

As always, my pleasure!

I wish you and your family the same!