Average of every 25 rows in a table

Hello,

I have a table of 10 columns and 1000 rows. I would like to take the average of each column for every 25 rows. How to code that please?

Thank you

Answer 1

[Abhishek Tiwari]

Hi,

This might work,

% Sample data
data = rand(1000, 10);

% Calculating Output Dimension (#columns will be same)
rows = 1000/25;
output = ones(rows, 10);

% Start first 25 entries then compute mean and increase index for next
% 25 entries
for row = 0:rows-1
    output(row+1, :) = mean(data(25*row+1:25*(row+1),:));
end
output

output = 40×10

0.5329 0.5851 0.5010 0.5203 0.4864 0.3876 0.5029 0.5378 0.4667 0.4931 0.5315 0.5217 0.5169 0.5313 0.5383 0.4457 0.4606 0.5541 0.4590 0.6092 0.4712 0.4571 0.4326 0.4300 0.5599 0.5561 0.5522 0.5662 0.5468 0.5205 0.4788 0.4865 0.4554 0.4486 0.5526 0.5052 0.3405 0.5116 0.5173 0.5189 0.4536 0.3814 0.5256 0.4594 0.4725 0.5219 0.5299 0.4808 0.4840 0.5354 0.3794 0.3971 0.4839 0.5850 0.3706 0.5975 0.6139 0.5391 0.3941 0.5435 0.5360 0.5580 0.5243 0.5750 0.4471 0.4273 0.5424 0.4981 0.4707 0.4634 0.4814 0.4900 0.6158 0.4795 0.4305 0.4495 0.4998 0.5014 0.4877 0.4645 0.4974 0.4583 0.4654 0.6242 0.4960 0.5045 0.4318 0.4466 0.3654 0.5716 0.4906 0.4275 0.3932 0.5329 0.5218 0.5332 0.4855 0.4368 0.3938 0.4639

[Reem RA]

I did not understand what you mean under % Calculating Output Dimension (#columns will be same), may you please elaborate? thanks

[Abhishek Tiwari]

Just defining dimension of output table... It is better than create one dynamically, saves time. When we average every 25 rows for each column dimension of output table is reduced from 1000 to 1000/25 (=40) but column remains same.

[Reem RA]

Thank you, I tried it and it worked.

Answer 2

[Akira Agata]

Another possible solution:

% Sample data
data = rand(1000, 10);

% Grouping
group = repelem(1:size(data, 1)/25, 25)';

% Apply mean function for each group
output = splitapply(@mean, data, group);

[Reem RA]

Can you please explain repelem(1:size(data, 1)/25, 25) what are you trying to do here?

[Akira Agata]

Hi @Rulla RA-san,

I just wanted to create "group number".

For more information, please take a look at the following.

https://www.mathworks.com/help/matlab/ref/splitapply.html#butc687-G

[Reem RA]

Thanks a lot, this worked well too!!!