How do I extract from array with values I got from that same array?

Question

Mo G 2023-3-9

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1926025-how-do-i-extract-from-array-with-values-i-got-from-that-same-array

回答： Voss 2023-3-9

I have ICA.txt file that has all the data (2 x 205) I need for this problem. I made a function that takes that data and uses the second column to find the peak.

function peak_indicies = peaks(height)
peak_indicies =[];
for i = 2:length(height)-1
if (height(i) > height(i-1))&&(height(i) > height(i+1))
    peak_indicies(end+1) = i;
else
    continue;
end
end

It works and I have 3 peaks, but I am stuck trying to extract both the second column and the first column so that I can plot those three points. I tried in script

peaktime = [];
while i = 1:205
if peak_indicies == ICA(:,2)
   peaktimes = i
else
continue; 
end
end

But this didn't work and I am not sure how else to do it. I tried

peaktimes = extract(ICA(ICA(:,2)==peak_indicies))

%Error using extract

%Not enough input arguments.

But also I am unsure how I would use that in this situation.

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Answer 1

Voss 2023-3-9

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1926025-how-do-i-extract-from-array-with-values-i-got-from-that-same-array#answer_1189675

在 MATLAB Online 中打开

% call peaks() to get the indices of the peak(s), based on the 2nd column of ICA:
peak_indices = peaks(ICA(:,2));
% get the 1st and 2nd column values (times and heights I guess) at those row indices:
peak_vals = ICA(peak_indices,:);
% or if you want them in two separate variables
peaktimes = ICA(peak_indices,1);
peakheights = ICA(peak_indices,2);