Extract data from multiple excel files

I am trying to extract data from a specific column from multiple excel files and save this columns in one table

D = 'C:\Users\Desktop\Analyze\';
for k=1:250
    file = sprintf('Data_%d.xlsx',k);
    filename = strcat('C:\Users\TR8E1MQ\Desktop\Analyze\',file);
    x = xlsread(filename);
    T = x(:,7);
end

This how I am extracting one column. I want to keep those and keep adding more values from other excel files.

Answer 1

[Guillaume]

I would recommend you use fullfile instead of strcat to build paths. This way you don't have to worry about path separators.

Assuming that all files have the number of rows, this is how I'd do it:

source_folder = 'C:\Users\Desktop\Analyze';  %much more meaningful name than D
numfiles = 250;
data = [];  %will be preallocated upon reading the first file, once we know the size of a column
for fileidx = 1:numfiles
    filedata = readmatrix(fullfile(source_folder, sprintf('Data_%d.xlsx', fileidx)));
    if fileidx == 1
        data = zeros(size(filedata, 1), numfiles);  %preallocate to the height of columns x num files
    end
    data(:, fileidx) = filedata(:, 7);  %copy column 7 into output matrix
    end
end

[Mariana]

Assumming all the files have the same number of rows?

[Guillaume]

Yes, since all columns of a matrix must have the same number of rows.

Otherwise, you'd have to pad the shorter rows / crop the longer ones / not use a matrix for storage. Any of these is possible.

[Mariana]

What is the other possibility for storage, in case of not using a matrix

[Guillaume]

A cell array, but be aware that a cell array is more complicated to use.

So, have your files got the same number of rows or not?

[Mariana]

No, all of the have different number of rows.

[Guillaume]

In that case:

source_folder = 'C:\Users\Desktop\Analyze';  %much more meaningful variable name than D
numfiles = 250;
data = cell(1, numfiles); %since all files have different number of rows. Store the desired columns in a cell array
for fileidx = 1:numfiles
    filedata = readmatrix(fullfile(source_folder, sprintf('Data_%d.xlsx', fileidx)));
    data{fileidx} = filedata(:, 7);  %copy desired column in corresponding element of the cell array
end 

[Mariana]

Is not working.

I received zha follwing error:

Undefined function or variable 'readmatrix'.

filedata = readmatrix(fullfile(source_folder, sprintf('Data_%d.xlsx', fileidx)));

[Guillaume]

For versions prior to R2019a, replace readmatrix by xlsread. Rest of the code would be the same.

[Mariana]

Thanks. You were right. Now, I have different cells and on each of them all of my values of that specific column are saved.

I would like to analyze these cells.

-Plot in a graph all of these values and find max. , min. and average values

How can I do this?

[Nusrat Chowhdury]

What is the code if I wanna take multiple columns of each excel file in the same way?