How to write for-loop?

Hello, Is it possible to create a for-loop which evaluates mean values of 12 (in my case) vectors, which has different dimensions? For example a=[1 2 3 5 4] and b=[1 1 2 5 6 8 9], find mean values using for-loop.

Thank you in advance. Sergey

Answer 1

[Kirby Fears]

Hi Sergey,

This sample code will do what you're looking for:

% sample of vectors
a=rand(10,1);
b=rand(9,1);
c=rand(8,1);

% vector names
vecs={'a','b','c'};

% pre-allocating vector of means
meanvec=NaN(numel(vecs),1);

% taking means
for iter=1:numel(vecs),
    meanvec(iter)=mean(eval(vecs{iter}));
end

However, this requires you to type out each variable name in "vecs". This operation would be much easier if you had stored all of your vectors into a cell to begin with, as I'm doing in the example below:

% sample of vectors
vecset=cell(3,1);
vecset{1}=rand(10,1);
vecset{2}=rand(9,1);
vecset{3}=rand(8,1);

% calculating mean of each vector
meanvec=cellfun(@(c)mean(c),vecset);

Hope this helps.

[Sergey Dukman]

Thank you, sir.

[Stephen23]

Store the vector in a cell array, and avoid using eval for such trivial code:

http://www.mathworks.com/matlabcentral/answers/196952-how-to-create-new-variables-in-batches-with-strcat

http://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

http://blogs.mathworks.com/loren/2005/12/28/evading-eval/

http://www.mathworks.com/matlabcentral/answers/51946-systematic-do-not-use-global-don-t-use-eval