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matrix creation from a loop

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Jonathan Demmer
Jonathan Demmer on 17 Sep 2020
Edited: Ruger28 on 17 Sep 2020
Hello all,
I would like to create 60 vector columns of zeros (6964,1) called lat_01_days, lat_02days, lat_03_days until 60. I know I could write them one by one but if i know How to create a loop to create them it would be better also for future research. Can someone help mep lease?
regards
Jonathan

  2 Comments

Stephen Cobeldick
Stephen Cobeldick on 17 Sep 2020
"I would like to create 60 vector columns of zeros (6964,1) called lat_01_days, lat_02days, lat_03_days until 60."
Numbering variables like that is a sign that you are doing something wrong.
Forcing meta-data (e.g. pseudo-indices) intoe variable names is a sign that you are doing something wrong.
"I know I could write them one by one ..."
Ouch!
"...but if i know How to create a loop to create them it would be better also for future research"
In fact what "would be better also for future research" is to avoid numbered variables entirely:
Jonathan Demmer
Jonathan Demmer on 17 Sep 2020
Thank you very much.

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Answers (3)

Walter Roberson
Walter Roberson on 17 Sep 2020
if i know How to create a loop to create them it would be better also for future research.
Our long experience is that it would make your future research worse instead of better.

  1 Comment

Jonathan Demmer
Jonathan Demmer on 17 Sep 2020
Thank you very much

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Stephen Cobeldick
Stephen Cobeldick on 17 Sep 2020
The simplest and most efficient solution is to just create one matrix:
lat = zeros(6964,60)
which you can then trivially access using indexing. There is no point in making it more complex than that.

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Ruger28
Ruger28 on 17 Sep 2020
Edited: Ruger28 on 17 Sep 2020
The two other answers are a more correct way of doing it. There is no need to create this many variables in your workspace. However, if you must...
You should use a structure instead of individual variables.
Blank_Vec = zeros(6964,1);
Num_Cols = 60;
for ii = 1:Num_Cols
name = sprintf('lat_%i_days',ii);
ZeroColStruct.(name) = Blank_Vec;
end
if you absolutely MUST have individual variables, one method is this:
% Removed due to being a terrible way to do something

  3 Comments

Stephen Cobeldick
Stephen Cobeldick on 17 Sep 2020
Do NOT follow this advice. It teaches a complex and inefficient use of MATLAB.
"However, if you must..."
"if you absolutely MUST have individual variables..."
Most of the situations that I have read on this forum where someone explains why they "must" use dynamic variable names it turns out to be simpler and more efficient to solve using other approaches. A not-very-well-informed-user's idea of "must" is unlikely to be very correct, based on many years of threads on this forum.
For basic tasks like the one shown in this question, I have yet to see any situation that is not better solved using the recommended approach of basic MATLAB indexing.
Jonathan Demmer
Jonathan Demmer on 17 Sep 2020
I am kind of new i understand what everybody else is saying above and i will follow your guidelines. Thank you very much.
Jonathan Demmer
Jonathan Demmer on 17 Sep 2020
Thank you Stephen for your advice.

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