d3.js：获取输入域范围之外的刻度值

Question

Given a list of values

var values = [245, 483, 498, 597, 726, 788, 799, 974];

I want to get tick values that "surround" the extent of the values domain:

// [200, 300, 400, 500, 600, 700, 800, 900, 1000]

Using the following does not work for this intent:

var scale = d3.scale.linear().domain(d3.extent(values));
var ticks = scale.ticks(9);
// [300, 400, 500, 600, 700, 800, 900] == ticks

That is no surprise since the D3.js reference says:

The returned tick values are […] guaranteed to be within the extent of the input domain.

Answer 1

Use .nice() :

var values = [245, 483, 498, 597, 726, 788, 799, 974];
var scale = d3.scale.linear().domain(d3.extent(values)).nice();
var ticks = scale.ticks(9);