Please help with Index exceeds matrix dimensions error

Question

Christopher Carey 2017-12-3

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https://ww2.mathworks.cn/matlabcentral/answers/370691-please-help-with-index-exceeds-matrix-dimensions-error

评论： Star Strider 2017-12-3

采纳的回答： Star Strider

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%%here is my code

clc; close all;

N=50;

x = zeros(1,N);

for n = 1:length(x)

    x(n)= sin((n/16)*pi);
end
y= zeros(1,N);
y(1)=-0.13;

for n = 2:length(x)

    y(n+1)=(-1/3)*x(n+2)+(1/2)*x(n+1)+(1/3)*x(n)+y(n);
end

stem(0:1:50, y, 'r-');

xlabel('n');

ylabel('y[n]');

title('Output y[n] of the system');

pause;

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Answer 1

Star Strider 2017-12-3

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/370691-please-help-with-index-exceeds-matrix-dimensions-error#answer_294381

在 MATLAB Online 中打开

This will eliminate the error:

for n = 2:length(x)-2
    y(n+1)=(-1/3)*x(n+2)+(1/2)*x(n+1)+(1/3)*x(n)+y(n);
end

however you have to change the stem arguments accordingly:

stem(0:1:49, y, 'r-')

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Christopher Carey 2017-12-3

thank you very much would you mind explaining how this fixes it please, I am a beginner at MATLAB.

Star Strider 2017-12-3

As always, my pleasure.

You are indexing x(n+2) in your code, and ‘x’ has only 50 elements. In order to avoid reading beyond the number of elements in ‘x’, you need to reduce the number of iterations by 2. Setting the iterations to 2:length(x)-2 accomplishes that, since ‘n’ now goes from 2 to 48.

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