loop of Column Average

I have a matrix of 1024 * 78.(datatype: double )

I want to average every two columns such that the resultant matrix must be 1024*39. (average of every two matrix)

how to get it done?

again for time being if i dont know the number of columns (due to huge dataset) and want to run a loop for averaging the columns for the similar case as mentioned about, what will be the changes in the code ?

Answer 1

[Davide Masiello]

There's no need to use a for loop.

Try the code below.

clear,clc

A = rand(1024,78);                      % initial matrix of doubles
B = (A(:,1:2:end-1)+A(:,2:2:end))/2;    % matrix of averages for each two columns

size(B)

ans = 1×2

1024 39

[Arvind Gauns]

Thank you @Davide Masiello.

it works

Answer 2

[Eric Delgado]

Hi @Arvind Gauns, just pass your input matrix to the function below. Hope it helps! :)

function outMatrix = Fcn_twoColumnsMean(inMatrix)

    arguments
        inMatrix (1024,:) {mustBeNumeric} = randn(1024, 78)
    end
        
    NN = floor(width(inMatrix)/2);
    outMatrix = zeros(1024, NN);
    
    for ii = 1:NN
        outMatrix(:,ii) = mean(inMatrix(:,2*ii-1:2*ii), 2);
    end
    
end

[Arvind Gauns]

' Error: Function definition are not supported in this context. Functions can only be created as local or nested functions in code files. '

this was the error encounted while using the above code.

[Eric Delgado]

It's not a script, but a function. You have to save the code as Fcn_twoColumnsMean.m or Fcn_twoColumnsMean.mlx (if your are using Live Script).

[Arvind Gauns]

If i have to integrate everything within a script then will this still be relevent?

[Eric Delgado]

For sure! Especially if the script is becoming too big. So... you have to create modules for debugging purposes. But at the end of the day, it's your call! :)

[Arvind Gauns]

in that case i need not need to call the function right ?