Update elements in matrix with condition

I have a large matrix (1st image). I need to update element in column 3&4 whenver it becomes 0 in column 5 or integer changes in column 6.

And I want to update it with sum from column 1 and 2.

See second image for more clarity.

My matrix should perform this for all the rows.

[Ravi Kumar]

Tried this, but not working. (still getting same values in column 3&4)

N = size(P,1);

for i = 1:1:N

if P(N,5) == 0

P(N,3) = P(N,1) + P(N,3);

end

end

Answer 1

[Cris LaPierre]

Use logical arrays (Ch 12 of MATLAB Onramp).

Perhaps something like this (untested)

P(P(:,5)==0,3)=sum(P(P(:,5)==0,[1,3],2));
P(P(:,5)==0,4)=sum(P(P(:,5)==0,[2,4],2))

Answer 2

[Rik]

N = size(P,1);
for k = 1:1:N
  if P(k,5) == 0
     P(k,3) = P(k,1) + P(k,3);
  end
end

Similar code will allow you to edit when the value changes:

if k>1 && A(k-1)==A(k)