Structures

I have loaded data that contain structures. The structures are of the form I have variable : struct1, struct2, struct3.... I have a 'file' with the list of these variables and want to manipulate the data contained in the structures with a for-loop.

Here is what I did:

      for i = 1:numel(files)
           data = files(i).data or data{1}.data
      some code;
end

I have errors like : Improper index matrix reference and other errors, Cell contents reference from a non-cell array object.

[Oleg Komarov]

Please rephrase ("I want to analyse each of the file by giving a text file containing the name of the structures that I want to analyse") and be more clear, maybe with an example of what you have and waht you'd like to achieve: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[Charles]

Thanks, I understand the question is poorly phrased and would make some corrections

Answer 1

[Oleg Komarov]

You could have the following structure:

s.myfield = 10;
s.another = 20;
s.hello   = 30;

Now suppose you have a list with the fieldnames which also happens to be the function to retrieve them from a structure:

fnames = {'myfield','another','hello'};

(Note that I didn't call the list with the name of the function)

Now you can manipulate the structure using dynamic fieldname indexing:

for n = 1:numel(fnames)
    tmp = s.(fnames{n});
    % do stuff with tmp or directly with s.(fnames{n}) 
end

This is a complete reference to manipulate structures: structures

[Charles]

Ho, thanks for your code. I also learnt some new terms like field name. Excuse me for my poor post, but my knowledge is still limited. However, to explain more with your code, fnames contains filenames and not fieldnames.

i.e

s.myfield = 10;

s.another = 20;

s.hello = 30;

t.myfield = 10;

t.another = 20;

t.hello = 30;

so fnames = {'s', 't',}

so my code is more like

for n = 1:numel(fnames)

tmp = fnames{i}.hello;

end

But it doesn't work. Thanks for your time.

[Jan]

@Charles: Please do not tell us, that "it doesn't work", but post a copy of the error message. Otherwise we waste too much time with guessing.

If fnames contains file names, load the files at first:

data = load(fnames{i}), disp(data.hello)

[Oleg Komarov]

How are the variables s and t being created or how are they stored?

If they're stored all in a .mat file then you could:

data = load(myfile.mat)

then

for...

data.(s{n})...

end

Answer 2

[Jan]

I'm not sure if this matchs your question, but similar question appear very often here:

If you use LOAD without catching the output to a variable, the output is directly written to the current workspace. Accessing these variables is probe to errors and often causes troubles, e.g. if a locally used variable is overwritten.

Therefore it is much safer and easier to use LOAD with catching the output:

data = load('File.mat');
field = fieldnames(data);
fprintf('  %s\n', field{:});
disp(data.field{1});

[Charles]

I guess I posed my question poorly.

I have variable : struct1, struct2, struct3....

I have a 'file' with the list of these variables and want to manipulate the data contained in the structures with a for-loop.

Here is what I did:

for i = 1:numel(files)

data = files(i).data or data{1}.data

some code;

end

I have errors like : Improper index matrix reference and other error.

[Jan]

"I have variable" and "I have a 'file'" is not clear. What is the type andthe contents of "files"? Please post the code completely by editing the original question - *not* as comment or answer. And append a complete copy of the error message, because "and other error" is not exact enough to give an advice.