Create a matrix from two matrices

Given two matrices

S = [1 2 1 2 1 3 4; 5 10 15 20 25 30 35];
G = [1 2 2 3 4 5 ; 7 10 15 20 25 30];

I want to create a new matrix GG where the first raw is given by the first raw of S merged with the one of G. While the second raw is the second raw of S plus the second row of G.

GG = [1 2 1 2 1 3 4 1 2 2 3 4 5; 5 10 15 20 25 30 35 42 45 50 55 60 65]

Note that wth the secnd row of S I arrive at 35, then I add 7 and arrive to 42. Then I don't want to add 10 but 10-7=3, and arrive at 42. I want always to add the difference between the term and previous one. considering that the first one (7) is just 7, cause it is 7-0=7.

May someone help me with this code?

Answer 1

[Stephen23]

>> GG = [S,[G(1,:);S(2,end)+cumsum(diff([0,G(2,:)]))]]
GG =
    1    2    1    2    1    3    4    1    2    2    3    4    5
    5   10   15   20   25   30   35   42   45   50   55   60   65