compute means between files

Hi,

I'm trying to create a series of vectors that stores the means from vectors located in a series of files. For example if file 1 (excel file) contains vector (1,2,3) and vector (4,5,6) while file 2 contains vector (7,8,9) and (10,11,12). I want to get vector 1 =(mean(1,7),mean(2,8),mean(3,9)) and vector 2=(mean(4,10),mean(5,11),mean(6,12)).

Any ideas on the shortest way to do this?

Answer 1

[Walter Roberson]

If the vectors are stored as columns in the files, each column a different vector, then

d1 = xlsread('FirstFile.xls');
d2 = xlsread('SecondFile.xls');
means = (d1 + d2)/2;

will then be vectors as a series of columns, each column the mean of the corresponding file columns.

If you have a number of files, say N of them, whose names are in "filenames" then

data = cell(N,1);
for J = 1 : N
  data{J} = xlsread(filenames{J});
end
means = mean(cat(3, data{:}),3);

[anna]

Thanks, I had originally tried that version (the 2nd one) and on selecting the column arrays from the original files I used something like this:

data = cat(3,data{:}); Mean1 = mean(data(:,2,:),3);

for example, to select column 2 from each of the files and calculate the means of those. These 2 lines would replace as in your comment:

means = mean(cat(3, data{:}),3);

But I am not getting the correct Mean1. It is a column vector but doesn't correspond to the right values. Am I not selecting them correctly?

[Walter Roberson]

My test data appears to get the right answer. Can you produce a small bit of sample data that it gets wrong?