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Turning separate columns of data into a single column or vector.

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Grace
Grace on 13 May 2019
Commented: Stephen Cobeldick on 14 May 2019
If I have a for loop looping through 12 files of data and I use the function A.data(:,1) in the loop to pull out the first column of each file, how do I turn those 12 columns into a single column. The first column in each file is the time column for the collected data; I want to string the time from each file together to make one long time vector with which I can make plots.
I will need to do this with every other column in the data aswell.

  2 Comments

Stephen Cobeldick
Stephen Cobeldick on 14 May 2019
The best solution is to follow the MATLAB documentation and use a cell array:
This will be more efficient than expanding an array in the loop, and will not give any warnings:
N = ... total number of files
C = cell(1,N);
for k = 1:N
C{k} = ... import one column of data
end
V = vertcat(C{:})

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Accepted Answer

Adam
Adam on 13 May 2019
times = [];
for ...
...
times = [ times; A.data(:,1) ];
...
end
You will get warnings about variable growing in a loop being slow, but if you are not able to presize them because you don't know how many rows there are in your files then you just have to ignore that. For 12 files it will likely be inconsequential anyway.

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