a(:,1) = [1 2 3 4 5]';
a(:,2) = [0.1 0.2 0.3 0.4 0.5]';
 
b(:,1) = [2 3 4 5 6 7]'; % neuer längerer Klassenvektor
b(:,2) = [0.1 0.1 0.2 0.5 0.3 0.4]'; % gesuchte Wahrscheinlichkeiten

          if min(a(:,1)) <= min(b(:,1))
             diff = min(b(:,1)) - min(a(:,1));
             a2 = a;
                   b2(:,1) = [a(1:diff,1); b(:,1)];
                   b2(:,2) = [zeros(diff,1); b(:,2)];
                   a2((length(a)+1):length(b2),1) = b2((length(a)+1):length(b2),1);
                   a2((length(a)+1):length(b2),2) = zeros;
                   b2((length(b)+diff+1):length(a2),1) = a2((length(b)+diff+1):length(a2),1);
                   b2((length(b)+diff+1):length(a2),2) = zeros;
                   class = a2(:,1);
                   prob  = a2(:,2)+b2(:,2);
            else
                 diff = min(a(:,1)) - min(b(:,1));
                 b2 =b;

                   a2(:,1) = [b(1:diff,1); a(:,1)];
                   a2(:,2) = [zeros(diff,1); a(:,2)];
                   b2((length(b)+1):length(a2),1) = a2((length(b)+1):length(a2),1);
                   b2((length(b)+1):length(a2),2) = zeros;
                   a2((length(a)+diff+1):length(b2),1) = b2((length(a)+diff+1):length(b2),1);
                   a2((length(a)+diff+1):length(b2),2) = zeros;
                   class = a2(:,1);
                   prob  = a2(:,2)+b2(:,2);
          end