To find the sum square of an array:
sumSquared = sum(array.^2);
If you have your arrays all together in a matrix:
% If each array is a colum of the matrix
sumSquaredEachArray = sum(matrix.^2, 1);
% If each array is a row of the matrix
sumSquaredEachArray = sum(matrix.^2, 2);
For finding the two lowest scores, let's assume that you have the scores in an array called "sumSquaredEachArray" (which would happen automatically if you have your arrays organized in a matrix)
% Get the order of lower to highest scores
[~, order] = sort(sumSquaredEachArray);
% Select the first two scores from the sorted order, which would be the lowest two
lowestTwoScores = order(1:2);
% Set those scores to "u3"
sumSquaredEachArrau(lowestScores) = u3;
