matlab - Assign value to the third column of a matrix for specific first and second column values -

the matrix a looks this:

1 1.1 0 2 1.2 0 3 1.3 0 4 1.1 0 5 1.5 0  1 1.0 0 2 0.9 0 3 0.3 0 4 0.1 0 5 0.4 0 

the first column represents x while 2nd represents y , 3rd z. see, x values gets repeated every 5 samples. , z column zeros, did calculation , want add value @ specific x , y value. how can ?

for example if want insert z = 5 value x = 4 , y = 0.1,

you do

maskrow = a(:,1) == 4 & a(:,2) == 0.1; a(maskrow,3) = 5 

explanation:

in first line of code, find rows of matrix satisfies both condition. i.e comparing x first column , y second column of matrix a. maskrow gives logicals of true corresponding row satisfies both above conditions while false rest of rows.

in second line of code, assign z values third column of particular row obtained rowmask