function c=castnum(i)
%  castnum.m - returns a 3 character string with the cast number 
%              for use with reading data files. 
%              string includes leading zeros for numbers less than 100.
%      needs variables set: none
%      sets variables: none
%      calls: none
%
if  i < 10 
  c=[ '00' num2str(i)];
elseif i < 100
  c=[ '0' num2str(i)];
else
  c=num2str(i);
end
