Indexing concatenated matricies without changing the order

Question

Elia 2014-10-30

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https://ww2.mathworks.cn/matlabcentral/answers/160688-indexing-concatenated-matricies-without-changing-the-order

评论： Abhiram Bhanuprakash 2014-10-31

I'm attempting to index an outputted matricy from one function into a bigger matricy. My code at the moment:

    % code
while j <= length(sec)
y=sec(j,:);
[max,~]=coros(y,thershold,x);
maxbox = [maxbox;max];
j=j+1;
end

The output max finds the largest values in a data set and outputs it as a matricy [x y]. Sample output:

if true
3 10
5 12
9 15
end

I then use maxbox = [maxbox;max]; to concatenate the matricies. I'd like to have each output correspond to the value of j it was found at. So that I know when they occur as well as where they occur. (j being time).

Sample of desired output:

if true
j 3 10
j 5 12
j 9 15
end

Before I concatenate it with the next matricy of values at j+1. Help is appreciated! Thanks.

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Answer 1

Abhiram Bhanuprakash 2014-10-30

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在 MATLAB Online 中打开

Hi Elia,

I guess you can use the 'ones' and 'size' functions to do this.

In your case, inside the 'while' loop, you can do:

maxbox = [maxbox;max];
temp = j*ones(size(maxbox,1),1);
maxbox = [temp maxbox];
j = j+1;
end

For documentation on 'ones' and 'size' functions, you can refer:

- ones: here

- size: here

Hope this helps,

Cheers!

Abhiram

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Image Analyst 2014-10-30

Please go ahead and give him "credit" by officially marking the answer as "Accepted". Then read this so you'll know how to format your posting properly.

Abhiram Bhanuprakash 2014-10-31