Set values in defined area on zero

This is my code and I attached the data file

load 'USS_w3'

USS_w3_POS = USS_w3(USS_w3>0);
MEAN = 2.5*mean(USS_w3_POS);

a = 1;
for z=1:length(USS_w3)

      if USS_w3(a) < MEAN
          a = a+1;
      else
          c = a;
          while USS_w3(c) > 0
              c = c+1;
          end
          USS_w3(a:c) = 0;
      end
  end

a = 1;
for z=1:length(USS_w3)

      if USS_w3(a) < MEAN
          a = a+1;
      else
          c = a;
          while USS_w3(c) > 0
              c = c-1;
          end
          USS_w3(c:a) = 0;
      end
  end