Calculating and extracting data from three dimensional array

Well I need to find the following things:

1. calculate the average score for each question, using all the data.
2. Extract data for question 3 for each year and create an array that compares question 3 from year 1 and year 2.

This is what i have so far:

%Create array of first and second year data
year1 = [3,6,4,10;5,8,6,10;4,9,5,10;6,4,7,9;3,5,8,10];
year2 = [2,7,3,10;3,7,5,10;4,5,5,10;3,3,8,10;3,5,2,10];
%Create 3-D array with two pages
testdata = cat(3,year1,year2)
%Calculate average for each question for each year in array
average = mean(testdata)

I'm not sure how to calculate the average of both arrays into one, and extract column 3 (question 3) from each year into one array. I know how to extract them separately but after that i don't know how to combine them. Any help would be great!

Answer 1

[Sven]

Almost there, Michael. Try this to average your two years:

average = mean(testdata,3)

This will average your testdata over the 3rd dimension. To extract the third column, just try:

average(:,3)
year1(:,3)
year2(:,3)

To extract the third column from testdata, use the following:

testdata(:,3,:)

This will result in a 3-by-1-by-2 matrix. Let us know if you were looking to do something slightly different.