How to change output in FOR Loop

Question

Finley Watson 2021-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/826305-how-to-change-output-in-for-loop

编辑： Jan 2021-5-10

Hello All,

I am in need of assisstance as my lecturer doesn't seem to know how to do what I want.

So, I need to create a loop that will change the output variable depending on the loop iteration. Sounds confusing so I'll put the code in and how I imagine it works. Apologies if it isnt actually possible but Ive been told it should be, just she doesnt know how to do it herself !

JanL = find(DateVector(:,2) == 1)';
FebL = find(DateVector(:,2) == 2)';
MarL = find(DateVector(:,2) == 3)';
AprL = find(DateVector(:,2) == 4)';
MayL = find(DateVector(:,2) == 5)';
JunL = find(DateVector(:,2) == 6)';
JulL = find(DateVector(:,2) == 7)';
AugL = find(DateVector(:,2) == 8)';
SepL = find(DateVector(:,2) == 9)';
OctL = find(DateVector(:,2) == 10)';
NovL = find(DateVector(:,2) == 11)';
DecL = find(DateVector(:,2) == 12)';

This what I have currently and want to shrink it into a loop. In my mind it works something like this:

X = [JanL FebL MarL AprL MayL JunL JulL AugL SepL OctL NovL DecL]
for k = 1:1:12
    X(k) = find(DateVector(:,2) == y)';
end 

Therefore producing the variable JanL with the datevector data accordingly. Doesnt work and I have no ideas how to do this after some substantial looking and investigating.

Any help much appreciated Thanks

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Walter Roberson 2021-5-10

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

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Answer 1

KSSV 2021-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/826305-how-to-change-output-in-for-loop#answer_696120

编辑：KSSV 2021-5-10

在 MATLAB Online 中打开

X = zeros(12,1) ; 
for k = 1:1:12
    X(k) = find(DateVector(:,2) == k)';
end 

The above is fine enough. You should go by indexing. X(1) means Jan, X(2) means Feb and so on....X(end) or X(12) means Dec. Read about indexing.

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Finley Watson 2021-5-10

Done that as the X array contains what I need as variables, see 'JanL' etc. But it now sees JanL as an unrecognised function or variable.

KSSV 2021-5-10

You need not to use string janL....your value for janL is nothing but X(1). Go by indexing, not by string.

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Answer 2

Jan 2021-5-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/826305-how-to-change-output-in-for-loop#answer_696195

编辑：Jan 2021-5-10

在 MATLAB Online 中打开

Creating variables dynamically has a lot of severe disadvantaged. Using a struct is nicer, safer and more efficient.

X = {'JanL', 'FebL', 'MarL', 'AprL', 'MayL', 'JunL', ...
     'JulL', 'AugL', 'SepL', 'OctL', 'NovL', 'DecL'};
Data = struct();
for k = 1:1:12
    Data.(X{k}) = find(DateVector(:,2) == y)';
end

By the way, all of the variables end with L. Is this really useful? Maybe it is better to read, if you call the struct "L" and the fields "Jan", "Feb", ...