how to load multiple files from directory into an array using matlab?

i have a directory that includes some .mat files , i want to load all these files into an array .

i tried something like this :;

x1=load('C:\Users\me\OneDrive\Desktop\project\a\first_file.mat')

x2=load('C:\Users\me\OneDrive\Desktop\project\a\second_file.mat')

... and so on for all the files in the directory , and at the end i want to have an array such that:

arr(1)=x1 ...

how can i access the directory and load all of the files at the same time into an array ?

ps: i tried using path before and dir but then i got this error :

> error using eval , undefind function 'workspacefun' for input

> arguments of type struct

thank you in advance.

[Walter Roberson]

Is there exactly one variable in the .mat file, and it has the same name in each case?

Is it a numeric row vector? Numeric column vector? 2D? 3D?

[molan]

each .mat file is a 2D matrix , and names are different but they all end with "_file" , for example :

first_file.mat

x_file.mat

...

(there are 11 files like those)

[Walter Roberson]

Are the variable names the same inside the file? Is there exactly one variable in the file?

Does it matter which order the entries go into the overall matrix?

Are there any .mat files in the directory other than the ones to be processed ?

[molan]

as i sayed each file is a matrix , each matrix has numbers regular numbers ,

i just want to put all of these files (which mean all of these matrixes ) into an array so it would be easier for me to have an access for them , the directory has only 11 files and there are no other files there , and the order doesn't matter at all

[molan]

also as i mentioned previously i did :

x1=load('C:\Users\me\OneDrive\Desktop\project\a\first_file.mat');

x2= ...

for all of the 11 .mat files ,

and then i did : matrices_struct=struct('matrix',{x1,x2 .....});

but this is not efficient because what if in the future i needed to do this to 100 files !

i just simply want to load all the files into an array , where then i can access each file using arr(i)

Answer 1

[Walter Roberson]

dinfo = dir('*.mat');
filenames = {dinfo.name};
for K = 1 : length(filenames)
    temp = load(filenames{i});
    FN = fieldnames(temp);
    FN1 = FN{1};
    thisdata = temp.(FN1);
    if K == 1
       all_data = thisdata;
    else
       all_data(:,:,K) = thisdata; 
    end
end

The code would be easier if they all had the same variable name (and the variable name was known.) This version of the code does not assume that they all have the same variable name. This code will not error if there is more than one variable in the file -- but if there is, then which variable is loaded might not always be the first alphabetically.

[molan]

Thank you very much , but i have a question , i can only run this code when i am in the directory .. how can i run this code when i am in another directory , because let’s say i want to add another directory that has other files and i want to load them into different array , but i don’t want to write a new script for each directory

I think i can do this using path and then dir( the path) but i can’t use path now because i get the error i mentioned in the question , is there another way ?

[Walter Roberson]

directory_to_process = 'appropriate_path_goes_here';

dinfo = dir( fullfile(directory_to_process, '*.mat') );
filenames = fullfile({dinfo.folder}, {dinfo.name});
all_data = [];

for K = 1 : length(filenames)
    temp = load(filenames{i});
    FN = fieldnames(temp);
    FN1 = FN{1};
    thisdata = temp.(FN1);
    if K == 1
       all_data = thisdata;
    else
       all_data(:,:,K) = thisdata; 
    end
end