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Sagar
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Using horzcat in a loop for combining large number of files

Asked by Sagar
on 27 Jul 2017
Latest activity Edited by Constance Woodman on 27 Jul 2017
hi, I need to combine 100 matrices horizontally using horzcat. I have a matrix named 'data' of size 20*30*100 in which 100 represents number of data granules for a day. I want to do the following: data_all = horzcat(data(:, :, 1), data(:, :, 2), data(:, :, 3) ................... upto 100). I want to do this in a loop since it is tedious to write all matrices from 1 to 100. Could you please suggest a quick way?

  1 Comment

I'm not super elegant at this but would think you would want to do it in one command rather than adding a column, then adding a column, etc., as a loop. I have been working with huge datasets and it can crash matlab on my older work machine when I make Matlab do extra work.
Maybe rather than horizontally concatenating in a loop, you could create a loop that writes the list for concatenation, then just insert the list?
I'm just sort of pseudo coding this out...
% initilize
x = total number columns
counter= 1
hugeFlippingString = empty string
% run loop
Loop until counter = total number of columns
append text to hugeFlippingString: "columnOrFileName", counter, ","
counter increment by 1
End loop
%Concatenate
giantMatrix = horzcat(hugeFlippingString)
% which actually does this: giantMatrix = horzcat(col1,col2, ... col100)

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1 Answer

Answer by James Tursa
on 27 Jul 2017
Edited by James Tursa
on 27 Jul 2017
 Accepted Answer

data_all= reshape(data,size(data,1),[]);
Or, if you needed to vertcat them instead, then you could use
result = reshape(permute(data,[2 1 3]),size(data,2),[])';

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