Apply the same function into several columns

Hi!

I have a matrix A (50x50), and every column of the 50 are different subjects. I want to apply the same function to each column separetely and save the answers of the function into a different matrix B(50x1) The function is exactly the same, all that changes is the data on which the function is performed on.

How can I do it?

Thanks!

Answer 1

[Guillaume]

Use a loop:

B = zeros(1, size(A, 2));
for column = 1 : size(A, 2)
    B(column) = yourfunction(A(:, column));
end

Or you can use cellfun, which is just a loop in disguise:

B = cellfun(@yourfunction, num2cell(A, 1));

edit: That's assuming the function cannot already operate on the columns of the whole matrix, as pointed out by Star.

[Jos (10584)]

I suggest the use of arrayfun, rather than cellfun, assuming yourfunction(V) returns a scalar value for a vector V:

B = arrayfun(@(k) yourfunction(A(:,k)) , 1:size(A, 2))

[Guillaume]

I find the cellfun more readable personally. Ultimately, you have the cost of an anonymous function call vs the cost of splitting the matrix into a cell array.

Answer 2

[MAK]

Thanks to all!!