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Combining consecutive vectors into a matrix

Asked by Lars Bouten on 2 Oct 2019
Latest activity Edited by Guillaume
on 2 Oct 2019
I am trying to combine 108 consecutive vectors (100x1 double) into a matrix in such a way that I will get a 100x108 matrix. The vectors are called like HH_1, HH_2, etc., so I can do it by using M=[HH_1,HH_2,...], but this is really a lot of work for 108 vectors. Therefore, I was wondering if there is a short and easy way to perform this action. After I obtain the 100x108 matrix, I want to seperate this matrix into 100 rows, how can I do this easily?

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I obtained these variables from a large database in which they all are filled in. So I did not make them myself via a code in Matlab.
But you do you get then into matlab? Are they already saved in a mat file?
I imported them from a .xlsx file via the Matlab import data wizard for Excel sheets.

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2 Answers

Answer by the cyclist
on 2 Oct 2019
Edited by the cyclist
on 2 Oct 2019
 Accepted Answer

You should very much try to work backward and try to get these dynamically named variables into MATLAB in a different way. For example, if you are somehow reading them in from a database via a for loop, maybe write directly into a matrix from there. Or something better than dynamically named variables!
Please read this tutorial.
But, if you are really, truly stuck with these variable names ... yes, you can work with them.
I will probably forfeit all of my Answers street cred for even mentioning eval, but ...
HH_all = zeros(100,108);
for nh = 1:108
eval(sprintf('HH_all(:,%d) = HH_%d',nh,nh))
end
will write each of your variables into a column of the new variable HH_all.

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Answer by Guillaume
on 2 Oct 2019
Edited by Guillaume
on 2 Oct 2019

You must have changed the options of the wizard to specifically create variables from the columns of the excel spreadsheet. Don't do that. Import the data as a table (best), or cell array and your problem will go away.
Or better, don't use the import wizard. Use readtable, readmatrix (if on a version new enough) or xlsread.
Obtaining your M matrix may be as simple as :
M = readmatrix(yourexcelfile);
If not, an example file would help us understand better.

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