Guide me what is wrong in this code,i am trying to retrieve 3 values from function and trying to place those values

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shalini vn 2019-4-23

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https://ww2.mathworks.cn/matlabcentral/answers/457928-guide-me-what-is-wrong-in-this-code-i-am-trying-to-retrieve-3-values-from-function-and-trying-to-pla

评论： shalini vn 2019-4-23

load('beamdata.mat');
fs=1000;
Nd=length(Az(:,1));
Ns=length(Az(1,:));
n=3;
w=zeros(Nd*n,1);
for i=1:1:Nd
    w((n*(i-1)+1):(n*i),1)=find_mode_freq(Az(i,:),fs,n);
end
function [w]=find_mode_freq(data,fs,n)
N=length(data(1,:));
data=fft(data,N);
pyy=data.*conj(data)/N;
pyy_half=pyy(1:(floor(N/2)+4));
f=(fs/N)*(0:(floor(N/2)+3));
[~,locs]=findpeaks(pyy_half,'sortstr','descend','minpeakdistance',20);
w=zeros(n,1);
for i=1:1:n
 w(i)=f(locs(i))*2*pi;
end
end

this error i am getting

Index exceeds the number of array elements (0).
Error in find_mode_freq (line 14)
 w(i)=f(locs(i))*2*pi;
Error in ex2 (line 11)
    w((n*(i-1)+1):(n*i),1)=find_mode_freq(Az(i,:),fs,n);

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Walter Roberson 2019-4-23

That .mat file would make it easier for us to debug the problem.

shalini vn 2019-4-23

https://in.mathworks.com/matlabcentral/fileexchange/52276-mode-shapes-extraction-by-time-domain-decomposition-tdd check this for beam data.

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采纳的回答

Walter Roberson 2019-4-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/457928-guide-me-what-is-wrong-in-this-code-i-am-trying-to-retrieve-3-values-from-function-and-trying-to-pla#answer_371801

The beamData Az (acceleration in the Z direction) starts out as all zero. There are no peaks in the first row, so findpeaks() returns empty. The code does not expect that.