Error using * Inner matrix dimensions must agree.

Question

misbah 0332 2015-3-4

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/181476-error-using-inner-matrix-dimensions-must-agree

评论： David Young 2015-3-4

    close all;
    clear all;
    clc;
    %x(n) = u(n) – u(n – 6)
    n1 = -1:1:6; %range of x-axis
    x1 = [zeros(1,1), ones(1,6),zeros(1,1)]; %signal at y-axis
    subplot(3,1,1); %subplot location
    stem(n1,x1); %discreet plot
    xlabel('time'); %labeling
    ylabel('Amplitude'); %labeling
    title('x(n) = u(n) – u(n – 6)'); %labeling
    %h(n) = 2^n {u(n) – u(n – 3)
    n2 = -1:1:3; %range of x-axis
    x2 = [zeros(1,1),ones(1,3),zeros(1,1)]; %signal at y-axis
    x2 = (2.^n2).*x2; %signal at y-axis
    subplot(3,1,2); %subplot location
    stem(n2,x2); %discreet plot
    xlabel('time'); %labeling
    ylabel('Amplitude'); %labeling
    title('h(n) = 2^n {u(n) – u(n – 3)'); %labeling
    x1k = fft(x1);
    x2k = fft(x2);
    y = x1k * x2k;
    y2 = ifft(y);
    subplot(3,1,3);
    stem(y2);

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David Young 2015-3-4

As you can see, your code is very hard to read. You can fix this by editing it and using the "{} Code" button.

David Young 2015-3-4

I think per isakson has done it for you.

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Answer 1

David Young 2015-3-4

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It's likely that this line

y = x1k * x2k;

should be

y = x1k .* x2k;

The * operator does matrix multiplication, but .* does array multiplication which is probably what you need here.

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misbah 0332 2015-3-4

same error :(

David Young 2015-3-4

Then I guess you need to give more information. That's the only occurrence of * in the code you have shown, so the error must be elsewhere. Please can you give the full error message, and say which line of code produces it.

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