Two Matrix array elements addition except the very first one

I have a matrix of 10x10000 and want to add previous column with current one excpoet the very first one like below:

First Row contents are suppose: a1 a2 a3 a4 .....

After Addition operation, new matrix result as: a1 a2+a1 a3+a2 a4+a3 .......

So a1 reamins a1. All other subsequent are added to prevoius column values for all rows in a series.

Sample non-working code that I generated is below:

N = 10; % 10 terminals in the TDMA system

TOTAL_SERVED_PACKETS = 100000;

num_arrivals = TOTAL_SERVED_PACKETS/N;

interarrival_time = exprnd(mean_interarrival, N, num_arrivals);

for arrival_loop = 2:num_arrivals %iterate through Interaarival time array for each station

for station_num = 1:N %iterate through the arrays for all stations

offset = 1;

arrival_list = interarrival_time(station_num,arrival_loop-offset)+interarrival_time(station_num,arrival_loop);

offset = offset + 1;

arrival_loop = arrival_loop + 1;

if station_num == N

end

if arrival_loop == num_arrivals

end

end

end

I am getting this error: Index in position 2 exceeds array bounds (must not exceed 10000).

Answer 1

[Prasanna Venkateshan]

matrix=[1 2 3 4;5 6 7 8;9 10 11 12];
for i=1:size(matrix,1)
  for j=size(matrix,2):-1:2
      matrix(i,j)=matrix(i,j)+matrix(i,j-1);
  end
end
disp(matrix)