Loading multiple mat files

Hello everyone, i want to load this 3 set of data files into matlab using for loop but it is not working for me. Any help...............

clear all;
close all;
clc;

datafile={'data1.mat' 'data2.mat' 'data3.mat'};
num_schemes=3;  
for sno=1:num_schemes
files = char(data(sno));
load files
end

[Ewunate Assaye Kassaw]

Thanks

Answer 1

[Stephen23]

You are getting confused between the command syntax and the function syntax. In particular you are trying to use the command syntax with a variable named files, which will never work as the line of code

load files

is interpreted as

load('files')

Where 'files' is treated as a string, not a variable. This is specifically explained in the load documentation: Do not use command form when any of the inputs, such as filename, are variables. The easiest solution is do not use the command syntax in your code, only use the function syntax and then you will never face this problem again. Try this instead:

filenames = {'data1.mat','data2.mat','data3.mat'};  
for kk = 1:numel(filenames)
    S = load(filenames{kk}) % Best to load into an output variable.
    ..
end

Also note that I fixed the cell array indexing to use the correct {} braces , removed the char operation which is completely unnecessary as the contents of the cell array filenames are already of class character, and for robustness loaded the file data into an output variable (which is a scalar structure).

[Aftab Ahmed Khan]

Thanks, it works.

[AUWAL ABUBAKAR]

Wow! Thanks alot Stephen. it works fine for me.

please how about if I have upto 500 files. must I type all the 500 file names?

Is there any way I can cut it short?

Thanks in advance

[Stephen23]

"must I type all the 500 file names?"

No.

"Is there any way I can cut it short?"

Either use dir or sprintf, as the MATLAB documentation shows:

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

[Wiqas Ahmad]

filenames = {'data1.mat','data2.mat','data3.mat'};

for kk = 1:numel(filenames)

load(filenames{kk})

end

Suppose in this case if I have three variables, for instance a,b and c in each data file and I want to execuate all these variables in my program from all data files, How can I code the program?

[Stephen23]

@Wiqas Ahmad: load the file data into an output variable (which is a scalar structure):

F = {'data1.mat','data2.mat','data3.mat'};
N = numel(F);
C = cell(1,N);
for kk = 1:N
    C{kk} = load(F{kk});
end
S = [C{:}];

You can access the data using indexing and fieldnames, e.g. the data from the second file:

S(2).a
S(2).b
S(2).c

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/generate-field-names-from-variables.html

[Arif Hoq]

Thank you very much @Stephen. it helped me a l lot. i have another query according to this.

S(2).a

S(2).b

S(2).c

above code can find the a,b,c from only file no 2.

1. any solution to get these variables a,b,c from all files in 1 matrix ? and
2. only variable 'a' from all 3 files?

[Stephen23]

@Mohammad Ariful Hoq: yes, use comma-separated lists:

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

For example, to get the 'a' variable from all files into one array:

a = [S.a] % or VERTCAT or HORZCAT

[Arif Hoq]

thank you very much@Stephen

Answer 2

[ELCIO S]

What about if I have many files with different names? How can I do to load all of them?

[Stephen23]

"What about if I have many files with different names? How can I do to load all of them?"

Use DIR or SPRINTF:

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