Linear scale nice function snapping to different values than ticks

[olly....@gmail.com]

I'm calling nice(5) and ticks(5) on a linear scale with a domain of [-4.09, 9.51]. The new domain is [-6, 10] with ticks in steps of 5: [-5, 0, 5, 10].

I would have expected the domain minimum to align with the lowest tick. Is there anything I can do to make this happen?

I did some investigating and found these strange results when niceing domains ranging from [-10,10] to [0,10]:

Starting min	Nice min
-5.3	-10
-5.2	-10
-5.1	-10
-5	-10
-4.9	-5
-4.8	-5
-4.7	-5
-4.6	-5
-4.5	-5
-4.4	-5
-4.3	-5
-4.2	-6
-4.1	-6
-4	-6
-3.9	-4
-3.8	-4
-3.7	-4
-3.6	-4
-3.5	-4
-3.4	-4

Looks like it jumps down to -6 for a while before going back up to -5 again. In some other testing I've found that it favours even numbers rather than snapping to multiples of 5 at this sized domain.

Sample code for the above:

for (var i = -10; i <= 0; i += 0.1)
  console.log("%f %s", i, d3.scale.linear().domain([i, 10]).nice(5).domain()[0])

[Mike Bostock]

Related issue: https://github.com/d3/d3-scale/issues/9