MATLAB: How to calculate averages for each rows from a specific column to a specific column in a matrix

averagecolumnsfor loopmeanrows

So, I have a large matrix (rows = 1000; columns = 1000) and I have to compute the averages of each rows, but not the whole, only 100 columns, each step.
Let me explain:
There is a given matrix.
A = 
1  2  3  4  5  6
7  8  9  10  11  12
13  14  15  16  17  18
19  20  21  22  23  24
25  26  27  28  29  30
31  32  33  34  35  36
In this case, I have to take the average of 2 columns (step by step) in each rows:
(1+2)/2   (3+4)/2   (5+6)/2
(7+8)/2   (9+10)/2  (11+12)/2
(13+14)/2 (15+16)/2 (17+18)/2  
...
The solution is a new matrix:
B = 
1,5  3,5  5,5
7,5  9,5  11,5
13,5  15,5  17,5
19,5  21,5  23,5
25,5  27,5  29,5
31,5  33,5  35,5
How can I code this to make the same results in bigger sizes (to calculate the average in each row by columns 1-100; 101-200; 201-300; etc…)?
Any idea is highly welcomend!
Thank you!

Best Answer

Here is one way, using the movmean function.
A = ...
[1  2  3  4  5  6
7  8  9  10  11  12
13  14  15  16  17  18
19  20  21  22  23  24
25  26  27  28  29  30
31  32  33  34  35  36];
NC = 2; % This is the number of columns you want to average over.
tmp = movmean(A,NC,2); % Note that the "2" here is dimension to average over, NOT the number of columns
B = tmp(:,NC:NC:end);
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