in matlab delete an entire row if the elements in certain columns equal zero

Question

I matlab I have a matrix of 4 columns. I want to delete an entire row if the elements in columns two, three and four all equal zero.

So, I think I need to do something l

Answer 1

% toy example
>> a = [1,0,0,1; 
        2,0,2,0; 
        3,0,0,0; 
        4,4,0,4; 
        5,0,0,0; 
        6,0,0,0; 
        7,0,7,0; 
        8,0,0,8; 
        9,0,0,0]; 

% solution
>> a(sum ( a(:, 2:4) == 0, 2) == 3, :) = []
a =
   1   0   0   1
   2   0   2   0
   4   4   0   4
   7   0   7   0
   8   0   0   8

I.e. if the sum of the number of zeros across columns 2 to 4 equals 3, delete that row.
(i.e. use logical indexing)