loading and storing specific field of many different file names of a struct

Hi everyone, I have a set of 100 readings from a test rig, all are multilevel struct .mat files. I am trying to group a specific field (which is common within all the files) into a single row matrix (100,:). So from the help of the Mathworks community i was able to load all the 100 files into one struct, but my real objective is to get a specific field,

folder_name=uigetdir(); 

filenameExtension='.mat';

TempMatrix=cell(100,1);

for n=1:100
    filename=[folder_name,'\exp_0',int2str(n),filenameExtension];
    TempMatrix{n,:}=load(filename);
    
end

all the files i want to load are named as exp_01.mat, exp_02.mat.......exp_0100.mat

the only way to accest the file I want is like this:

example for exp_02:

FinalMatrix=[TempMatrix(2).data.exp_02.Y(3).Data];

so u see i need to change the file name each time to get the answer. But how do i get it in a for loop to store all the 100 files target field(Y(3)) into a single array matrix for ease of access.

Any help/advice would be realy appreciated. Thank you.

iv attached few example files.

[madhan ravi]

have you seen getfield()?

[Kirankumar Thangadurai]

yea i tried this but gives error

[Stephen23]

"...i was able to load all the 100 files into one struct,"

But your code does not show this at all. it shows you loading lots of separate scalar structures into one cell array (the badly named TempMatrix).

Answer 1

[umichguy84]

When using structures you can use variables and expressions to access fields using () . For instance lets say you had the following.

x.b1=1;
x.b2=2;

y = zeros(2,1)
% You can access the fields in a loop by using ()
for i=1:2
    y(i)=x.(['b' num2str(i)]);
    
end

So assuming I'm understanding your problem correctly you could do:

filename = ['exp_0',int2str(n)];
FinalMatrix=[TempMatrix(2).data.(filename).Data];

[Kirankumar Thangadurai]

Thank you this seemed to solve the problem.

Answer 2

[Stephen23]

Method one: dir and a structure array:

D = uigetdir();
S = dir(fullfile(D,'*.mat'));
for k = 1:numel(S)
    S(k).import = load(fullfile(D,S(k).name));
end

Then you can access the data using indexing, e.g. for the second file:

S(2).import.data

Method two: sprintf and a cell array:

D = uigetdir();
N = 100;
C = cell(1,N);
for k = 1:N
    F = sprintf('exp_%03d.mat',k);
    C{k} = load(fullfile(D,F));
end
S = [C{:}]; % optional: convert cell array to single structure

Then you can access the imported data using indexing, e.g. for the second file:

C{2}.data
S(2).data % optional: if converted to single structure.

You should also read these:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[Kirankumar Thangadurai]

Thank you so much for all your effort, it was very useful to improve my code and sorry about the bad naming, I was just trying it out roughly.