Create a new array by summing the columns of old array

I have an array that is 512x64, I would like to sum each consecutive columns until I have a new array that is 512x32,

so old_array column 1 + old_array column 2 = new_ array column 1

old_array column 3 + old_array column 4 = new_ array column 2

old_array column 5 + old_array column 6 = new_ array column 3

etc.

I have tried using a nested for loop but I am unsure what to exceute inside. Thank you for any help!

Answer 1

[Stephen23]

The MATLAB approach, where M is your matrix:

new = M(:,1:2:end) + M(:,2:2:end);

[Shanice Kelly]

Thank you!

Answer 2

[Walter Roberson]

reshape( sum( reshape(YourArray, 512, 2, 32), 2), 512, 32)

[Shanice Kelly]

Thank you!

Answer 3

[Daniel Catton]

a = YourArray;
b = [];
for i = 1:2:32
    b = [b a(:,i)+a(:,i+1)];
end

[Shanice Kelly]

Thank you!

Answer 4

[Michael]

By calling up the matrix elements using their linear indices and skipping by the number of rows in your matrix you can do what you are trying. I have a simple example below using a 2x10 matrix that produces a 2x5 result. Note that this isn't the most efficient method, as it does some summations that aren't necessary and just throws them away in the last line of code. Unless you are worried about speed or memory, this is probably just fine though. I hope this helps.

%Build the matrix
blah = [1  2  3  4  5  6  7  8;...
        9 10 11 12 13 14 15 16];

%Get sizes
[rows,cols] = size(blah);
els = numel(blah);
%Create an list of the linear indices of blah that excludes the last column
allbutlastcol = 1:(els-rows);
%Do the summation, but get the result as a vector
%(Here is where we skip with the +rows)
blahsum_vector = blah(allbutlastcol)+blah((allbutlastcol)+rows); 
%Reshape the result to get the matrix result
blahsum_matrix = reshape(blahsum_vector,rows,cols-1);
%Remove the columns we don't need
result = blahsum_matrix(:,1:2:end)

result =

     3     7    11    15
    19    23    27    31