Divide the maxvalue by the number of lines in your grid, throw away the remainder, add 1 to the result, this gives you a value w/o decimals that will work. for 'rounding' create a lookup table e.g <2 make 2; >2,<5 make 5 etc. Most uP graph apps have a narrow range of graph values; however if your variance i colonormous, divide values >100 by 100, multiply the result of the lookup by 100 etc.
Happy Holidays,

Erik Malund