# matrix creation from a loop

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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

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 on 17 Sep 2020
Thank you very much.

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 on 17 Sep 2020
Thank you very much

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.

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

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 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 on 17 Sep 2020