MATLAB: Creating an array from a loop

Question

I have a list idx=[1 3 5 12].Every index represents an area in separate_areas list.For example separate_areas(3)=1615.

I want to create 2 lists:

a) an AreasList [separate_areas(10),separate_areas(3),separate_areas(5),separate_areas(12)]

using a for loop through idx

b) an ErrorList in which i substract all the combinations of the elements of the created AreasList.

The length of the ErrorList will be length(AreasList)!(factorial)

Answer 1

Try this (requires the Statistics and Machine Learning Toolbox for pdist2)

% Specify selected indexes.
indexes=[1 3 5 12]
% Every index represents an area in separate_areas list.
% Create sample data.
separate_areas = randi(10000, 1, 15)
% Get subset of separate_areas
areasList = separate_areas(indexes)'
% Use pdist2 to get differences between all the areas.
xy = [areasList, ones(length(areasList), 1)]
errorList = pdist2(xy, xy)

pdist2() is the function that does all the combinations of subtractions that you want. It shows:

areasList =
        6020
        6541
        7482
        5384
xy =
        6020           1
        6541           1
        7482           1
        5384           1
errorList =
           0         521        1462         636
         521           0         941        1157
        1462         941           0        2098
         636        1157        2098           0