tickStep function Ticks
Returns the difference between adjacent tick values if the same arguments were passed to ticks: a nicely-rounded value that is a power of ten multiplied by 1, 2 or 5.
Note that due to the limited precision of IEEE 754 floating point, the returned value may not be exact decimals; use d4_format to format numbers for human consumption.
Implementation
num tickStep(num start, num stop, num count) {
final reverse = stop < start,
inc = reverse
? tickIncrement(stop, start, count)
: tickIncrement(start, stop, count);
return (reverse ? -1 : 1) * (inc < 0 ? 1 / -inc : inc);
}