Martix help within a for loop

Hello,
I have a 2 by 1000 matrix.  I want to wrtie and if statement saying if A(2,:)=1 then to spit out the corresponding A(1,:) value.  Once i have all my A(1,:) values that correspond to A(2,:) = 1, i will add them all.

Answer 1

[Image Analyst]

Try this:

% Create random sample data.
m = int32(randi(9, [2, 1000]))
% Find out which columns have a 1 in row 2
columnsThatAre1 = m(2, :) == 1
theFirstRowvalues = m(1, columnsThatAre1)
% Sum them up
theSum = sum(theFirstRowvalues)

It should be self-explanatory and easy to follow with comments and descriptive variable names. Of course you could do it all in one compact line, but I thought you'd find this easier to follow.