calculating the average from a large excel file

Hi again,

I have a really large excel file which I have imported in Matlab.

So it's a large array with dimensions : 588845x10 double

how can I get the average value from the first 48 values, then the average from the the next 48 values and so on?

many thanks,

Nikolas

Answer 1

[Guillaume]

 >>588845/48
 ans = 
      12267.604

The number of rows is not divisible by 48. What are you planning to do with the last few rows?

Assuming you have a number of rows divisible by 48, the easiest is to reshape the matrix into 48 rows, and take the mean along the rows.

m = reshape(1:5888450, 588845, 10);   %demo data, replace by your own matrix
croppedm = m(1 : size(m,1)-mod(size(m, 1), 48), :);  %crop number of rows to multiple of 48
meancroppedm = squeeze(mean(reshape(croppedm, 48, [], size(m, 2)), 1))  %mean along rows

The mean of the last portion:

meancutm = mean(m(size(m, 1)-mod(size(m, 1),48) : end, :), 1)

The two combined

mean48 = [meancroppedm; meancutm]

[Nikolas Spiliopoulos]

it works!! thanks a lot!