Reasonable optimized chart scaling

Question

I need to make a chart with an optimized y axis maximum value.

The current method I have of making charts simply uses the maximum value of all the graphs, then

Answer 1

You could use div and mod. For example.

Let's say you want your chart to round up by increments of 20 (just to make it more a more arbitrary number than your typical "10" value).

So I would assume that 1, 11, 18 would all round up to 20. But 21, 33, 38 would round to 40.

To come up with the right value do the following:

Where divisor = your rounding increment.

divisor = 20
multiple = maxValue / divisor;  // Do an integer divide here. 
if (maxValue modulus divisor > 0)
   multiple++;

graphMax = multiple * maxValue;

So now let's plugin real numbers:

divisor = 20;
multiple = 33 / 20; (integer divide)
so multiple = 1
if (33 modulus 20 > 0)  (it is.. it equals 13) 
   multiple++;

so multiple = 2;
graphMax = multiple (2) * maxValue (20);
graphMax = 40;