2d to 3d array conversion

I have 14641 csv files each of dimension 257x7. I need to convert it to a 3d array of dimension 257x7x14641.

I generated an array of 1x14641 dimension each element having 257x7 dimension by the following code snippet:

for i=1:14641
a{i} = readtable(strcat('output_',num2str(i),'.csv'));
end

I thought of trying 'presume' and 'reshape' functions. They are throwing an error saying "Cell contents reference from a non-cell array object".

Then, I tried 'cat' function. It is throwing error "Duplicate variable name: alpha" as I have column headings in every csv file.

Should I continue this approach? How to overcome there errors? Or is there an alternative approach?

P.S.: A sample csv file is attached.

Answer 1

[Ameer Hamza]

First convert tables to arrays and then use cat()

for i=1:14641
a{i} = readtable(strcat('output_',num2str(i),'.csv'));
end
a = cellfun(@table2array, a, 'UniformOutput', false);
M = cat(3, a{:}); % concatenate in 3rd dimension

Or newer vesrions, you can directly use readmatrix and then use cat()

for i=1:14641
a{i} = readmatrix(strcat('output_',num2str(i),'.csv'));
end
M = cat(3, a{:}); % concatenate in 3rd dimension

[J Sujatha]

Thanks for your prompt reply.

Firstly, I got error saying "Error using cellfun. Non-scalar in Uniform output, at index 1, output 1. Set 'UniformOutput' to false."

I rectified it by:

a = cellfun(@table2array, a, 'UniformOutput','false')

Now I am getting error "Error using cellfun. Input #4 expected to be a logical value for the parameter 'UniformOutput'."

I am unable to get over it.

[Ameer Hamza]

Please check the updated answer.

[J Sujatha]

Thank you! As per the updated answer, now, I'm getting "Error using table2array (line 27). Cannot concatenate the table variables 'R' and 'Zc', because their types are double and cell."

[Ameer Hamza]

It means that all your table columns are not of the same type. For example, some are strings. In that case, you cannot create a 3D array. MATLAB arrays must have all elements of the same class. However, you can create a cell array in this case. Change the line to

a = cellfun(@table2cell, a, 'UniformOutput', false);

[J Sujatha]

It's completely working! Thanks a lot!!

[Ameer Hamza]

I am glad to be of help!!!