NEED HELP with fir1

clc;

clear all;

f1 = 100;

f2 = 300;

f3 = 800;

fs = 5000;

m = (0.3*f1)/(f2/2);

M = rand(8/m);

N = M-1;

b = fir1(N,25*f2/(fs/2));

fig(1)

[h,f]= freqz(b,1,512);

plot(f*fs /(2*pi), 20*log10(abs(h)))

xlabel('frequency/Hz'); ylabel('/db');

title('Gain response of band pass filter');

axis [0 0.1 -22];

subplot [3 1 2];

Fs = fft (s,4096);

Afs=abs(Fs);

f = (0:255)*fs/4096;

plot(f,Afs(1:256));

xlabel('Frequency/Hz');ylabel('Amplitude')

title('Frequency domain diagram before filtering')

figure(3)

sF =fft(s,4096);

sf =filter(b,1,5);

subplot [3 1 3];

plot(t,sf)

xlabel('/s');

ylabel('Amplitude')

Afsf = abs(Fsf);

f=(0:255)*fs/4096;

plot(Afsf(1:256))

xlabel('Frequency/Hz');

ylabel('Amplitude')

need help with fir1

[John D'Errico]

When you have a question, is there a good reason why you would post a PICTURE of your code? Instead, all you needed to do was to paste in the text itself, complete with the error message. At least you included that.

But by posting only a picture of your code, we cannot now copy that into MATLAB, to show you what you did wrong. We need to retype it from scratch. In fact though, it is actually easier to just paste in text, so you did this the hard way for yourself, and you decreased the fraction of people who might be willing to help you.

Is there a good, valid reason why you want to make it more difficult for someone to help you?

[Justin tran]

Sorry about that. I pasted the code in text for you to use. My apologies

Answer 1

[Paul]

Hi Justin,

Executing the top part of the code ...

f1 = 100;
f2 = 300; 
f3 = 800;
fs = 5000;
m = (0.3*f1)/(f2/2);
M = rand(8/m);
N = M-1;

For fir1 to work, N must be an integer scalar. It's not a scalar, and the elements of N are not integers.

size(N)

ans = 1×2

40 40

N(1,1)

ans = -0.5760

For fir1 to work, the second argument has to be between 0 and 1. It isn't.

25*f2/(fs/2)

ans = 3

%b = fir1(N,25*f2/(fs/2));

Can you provide more insight into what you're trying to accomplish with this code?

[Walter Roberson]

Note that rand() with a single parameter returns a square matrix, not a vector.