function data_back = clean_invalids(data, bad, arg)

% This function takes an array, and converts invalid numbers to NaNs.
%   data:       array to be cleaned
%   bad:        value that corresponds to an invalid entry
%   arg:        = 1 if data>bad is test for invalid
%               = 2 if data<bad is test for invalid
%               = <1 if abs(data-bad) < arg is test for invalid...