MATLAB: Question about extracting a structure field using eval

eval

hi! I am extracting the fields of a structure using the following code

    names = fieldnames(BD); 
    for ii = 1: length(names)
        eval([names{ii} '=BD.' names{ii}]);
    end

and it works but I get all the extracted arrays and data shown in the commend window also, any suggestion how to avoid this ?! thank you!

Best Answer

Do NOT use eval for such trivial code. This way of accessing structure fields has been obsolete for more than ten years, as you will learn when you read the MATLAB blogs.

Use dynamic fieldnames instead:

names = fieldnames(BD); 
for ii = 1:numel(names)
    names{ii} = BD.(names{ii});
end

Or learn how to use MATLAB efficiently and use struct2cell:

out = struct2cell(BD);

Related Solutions

MATLAB: How to change struct name in a loop

Although there is a MATLAB function to do this, but it is a very bad practice to name your variables like this. It will make your code error prone and hard to debug. Therefore I am going to suggest the correct way to solve the problem. You should create a struct array and store the input number as a field of the struct. For example

for ii=1:10
  X = input('which individual? ');
  s(i).individualNumber = X;
  s(i).length = ...;
end

It will take 10 inputs from user and store them in struct array.

MATLAB: Dynamic fieldnames

Your code is a little confusing because it doesn't appear that you are assigning anything to the structure. Here is code that does assign values to the structure:

names = {'danny';'edgar';'larry'};
field = {'one';'two';'three'};
for ii =1:length(names)
    Newstruct.(names{ii}).(field{ii}) = ii;
end

This is how I am interpreting your code. It could be that you mean this instead (or switch names and field...):

names = {'danny';'edgar';'larry'};
field = {'one';'two';'three'};
for ii =1:length(names)
    Newstruct.(names{ii}) = field{ii};
end

If these aren't what you mean, please create one top level of the new structure by hand and show the code. Then perhaps we can figure out how to make it from names and values.

Best Answer

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MATLAB: How to change struct name in a loop

MATLAB: Dynamic fieldnames

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