My matlab plot is blank when I plot

Hello all,

The plot opens up with all the appropriate labels, but the actual line does not show up. I have tried switching the 'w' and 'f' in the function H1 and H2 when I try to plot.

f = -100:0.1:100;
w = 2*pi*f;

H1 = @(s) (s.^2 + 98010.65) / (s.^2 + 52.36*s + 98010.65);

subplot(2,1,1)
plot(f,abs(H1(j*w)),'k')
grid on
%xlabel('2*pi*f')
%ylabel('|H_1(j*2*pi*f)|')

subplot(2,1,2)
plot(f, angle(H1(j*w)))
grid on
%xlabel('2*pi*f')
%ylabel('<H_1(j*2*pi*f)')

Answer 1

[David Goodmanson]

Hi Henry,

In the definition of H1, use

./ instead of /

so you get term-by-term division. To spot the error, one straighforward thing to do Is define a new variable

z = H1(j*w)
subplot(2,1,1)
plot(f,abs(z),'k')

This puts z into the workspace and allows you to see that it is a scalar, so it will not plot vs. f. That puts you on the hunt for a particular kind of error in H1.

In this situation I did not get there using the debugger. Maybe someone with more expertise than I have with using the debugger on anonymous functions will weigh in on how to do it.