Remove for-loop by using cellfun

var_name = {'A','B','C'};

for i=1:length(var_name)
   eval([cell2mat(var_names(i)) '=zeros(10,1);'])
end

How can I do?

Thanks in advance

[Cedric]

Approaches involving dynamic variable naming are almost always flawed. I think that you/we should work upstream and change the approach so you don't have to use EVAL and dynamic names. What are you trying to achieve overall, and where/how are these A, B, and C variables defined?

[Christophe]

The objective is to make preallocation for about 106 variable (which are double).

[Cedric]

If all "variables" contents are 10x1 numeric arrays, it would be much more natural/efficient (and simpler) to build an array of zeros. For 3 "variables", for example:

 nData = 3 ;
 data  = zeros( 10, nData ) ;

and then use e.g.

 data(:,2) = ...

to get the column vector for the second data.

Answer 1

[James Tursa]

You can't avoid the for loop. Either it will be explicitly in your code, or whatever MATLAB function you use will have it in the background. It isn't a big deal in your case, so I would just advise keeping it explicit. Makes your code more readable anyway. E.g.,

z = zeros(10,1);
for i=1:length(var_name)
   eval([var_names{i} '=z;'])
end

The reason for doing the "z = zeros(10,1)" up front is to create shared data copies of the 10x1 zeros matrix instead of individual ones. For you small example (106 variables) it won't make any practical difference in timing, but I thought I would include this option just for completeness of the example.

Answer 2

[Robert Cumming]

Create the dynamic variables inside a struct instead of using eval

 var_name = {'A','B','C'};
 for i=1:length(var_name)
  myStruct.(var_name{i}) = zeros(10,1);
 end

[Christophe]

The objective is not to use struct.

Thanks for you answer

Answer 3

[the cyclist]

I suggest you read this document for some suggestions.

Answer 4

[the cyclist]

Please tell us you are not naming those 106 variables A,B,C, ..., AA, AB, AC, etc!

Could you do this via a cell array instead?

for n = 1:106
  A{n} = zeros(10,1);
end

and use those as your variables?

[Christophe]

I'm not naming these variables A, B, C ... Variables names have already been defined by another user. These varaibles names are linked to another software (AMESIM from Siemens/LMS) & here is few examples: injector_delay, mass_fuel ... I want to use vectorization to avoid for-loop & I think we can use cell2fun but I don't know how to

[John D'Errico]

Changed zeros{10,1} to zeros(10,1).