[julia-users] find nearest non-zero element in matrix

[tcs]

Hi julia-users,

I am looking for a function that takes a two-dimensional matrix and a set 
of matrix indices as inputs and spits out the nearest non-zero element in 
taxicab distance over the matrix index. 
I am asking for your advice because this function needs to be very fast as 
I have to do this search many times. Any ideas or advice would be greatly 
appreciated.

Thanks!