problem with my code please !!

Hi guys , How I can solve this error in my code see the attach file

the error appear in last four lines ...

[Abdullah AlHarbi]

the file is here ...

[Star Strider]

Your code ran for me without error (in R2016a).

What error did it throw when you ran it?

[Abdullah AlHarbi]

last four lines see it in command window

[Ced]

lol, it would be rather scary if he you see your command window. You could just post the error message... But see my answer below.

[Abdullah AlHarbi]

this is the error

Matrix dimensions must agree.

Error in MATLAB_ASSIMENTS (line 71) x=x1+x2+x3;

[Star Strider]

You need to create those vectors to be the same lengths. Consider using the linspace function.

[Walter Roberson]

Star Strider: is it possible that you are using the R2016a pre-release rather than the full version? There were some experimental changes in R2016a pre-release that were moved again before the full version.

[Star Strider]

Hi Walter,

I’m running the full R2016a. By mistake, I didn’t scroll all the way down, so I didn’t run the full code the first time. When I ran all of it, I got the error, and suggested linspace in the event the limits were described but the vector length was not. (We don’t know.) If it’s necessary to use the colon operator to create the vectors, and the limits are fixed, then I don’t see a solution.

We probably need to see the problem statement in order to attempt an Answer, which is the reason I didn’t.

Answer 1

[Ced]

Interesting, not sure how matlab 2016 handles this. I am getting a "Matrix dimensions must agree" error, and for good cause.

In short:

You need to define n1, n2, n3 such that they all have the same length.

In detail:

in line 17: x1 has length 10

n1 = 6:15;
x1 = [ones(1, 10)]; % what you had
% x1 = 1:length(n1); % My suggestion

line 25/26: x2 has length 5

n2 = 1:5
x2 = (1/3).^n2

line 33/34: x3 has length 20

n3 = 1:20
x3 = cos (pi*n3/4)

In line 71, you try to add all three, but matlab does not know how to add three vectors of different lengths.

Answer 2

[John BG]

subplot has 3 indices. Changing your subplot indices as follows then it doesn't return error:

n=1:20
h=3*(-1/4).^n
;subplot(4,2,1);stem(n,h)
xlabel('Sample');ylabel('Amplitude');title('h[n]');

%(b)  Calculate the output of this system for following inputs;
%1.  x1[n] = u[n-5]          1 ? n ? 10
n1 = 6:15;
x1 = [ones(1, 10)];
subplot(4,2,2);stem(n1, x1)
xlabel('Sample');ylabel('Amplitude');title('x1[n]');

%2.  x2[n] = (1/3)^n u[n]    1 ? n ? 5
n2 = 1:5
x2 = (1/3).^n2
subplot(4,2,3);stem(n2, x2)
xlabel('Sample');ylabel('Amplitude');title('x2[n]');

%3.  x3[n] = cos (pi*n/4)    1 ? n ? 20
n3 = 1:20
x3 = cos (pi*n3/4)
subplot(4,2,4);stem(n3, x3)
xlabel('Sample');ylabel('Amplitude');title('x3[n]');

%The Output 
%y1
y1 = conv(x1,h);
subplot(4,2,5);stem(y1)
xlabel('Sample');ylabel('Amplitude');title('y1');

%y2
y2 = conv(x2,h);
subplot(4,2,6);stem(y2)
xlabel('Sample');ylabel('Amplitude');title('y1');

%y3
y3 = conv(x3,h);
subplot(4,2,7);stem(y3)
xlabel('Sample');ylabel('Amplitude');title('y3');

If you find this answer of any help solving your question, please click on the thumbs-up vote link,

thanks in advance

John

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