how to categorize into 0 and 1 an array

I'm trying to create a neighborhood array based on a search radius. I have the matrix of symmetrical distances d, a minimum distance value calculated "minimum distance", and the maximum radius "r" to where it will be considered neighbor. How do I create a neighborhood array considering the radius r = 2 * sqrt (2) * minimum_mini distance? I want to categorize for 1 where it is less than or equal to r and for 0 where it is greater than r. I could not build a function using the distance matrix. Please help me! Thank you