Non-linear quantitative scales are slightly more accurate. [Log tick formatting](https://github.com/d3/d3-scale#log_tickFormat) now assumes a default *count* of ten, not Infinity, if not specified. Log scales with domains that span many powers (such as from 1e+3 to 1e+29) now return only one [tick](https://github.com/d3/d3-scale#log_ticks) per power rather than returning *base* ticks per power.
[Sequential scales](https://github.com/d3/d3-scale#scaleSequential), are a new class of scales with a fixed output [interpolator](https://github.com/d3/d3-scale#sequential_interpolator) instead of a [range](https://github.com/d3/d3-scale#continuous_range). Typically these scales are used to implement continuous sequential or diverging color schemes. Inspired by Matplotlib’s new [perceptually-motived colormaps](https://bids.github.io/colormap/), 4.0 now features [viridis](https://github.com/d3/d3-scale#interpolateViridis), [inferno](https://github.com/d3/d3-scale#interpolateInferno), [magma](https://github.com/d3/d3-scale#interpolateMagma), [plasma](https://github.com/d3/d3-scale#interpolatePlasma) interpolators for use with sequential scales. Using [d3.quantize](https://github.com/d3/d3-interpolate#quantize), these interpolators can also be applied to [quantile](https://github.com/d3/d3-scale#quantile-scales), [quantize](https://github.com/d3/d3-scale#quantize-scales) and [threshold](https://github.com/d3/d3-scale#threshold-scales) scales.
You can now control whether an ordinal scale’s domain is implicitly extended when the ordinal scale is passed a value that is not in its domain. By default, [*ordinal*.unknown](https://github.com/d3/d3-scale#ordinal_unknown) is [d3.scaleImplicit](https://github.com/d3/d3-scale#scaleImplicit), and unknown values will be added to the domain:
4.0 also ships new Cubehelix schemes, including [Dave Green’s default](https://github.com/d3/d3-scale#interpolateCubehelixDefault) and a [cyclical rainbow](https://github.com/d3/d3-scale#interpolateRainbow) inspired by [Matteo Niccoli](https://mycarta.wordpress.com/2013/02/21/perceptual-rainbow-palette-the-method/):
By setting *ordinal*.unknown, you can instead define the returned output for unknown inputs:
new ordinal scale API!
new *ordinal*.unknown lets you control whether the domain is implicitly extended.
d3.scaleOrdinal constructor now takes an optional *range*.
new d3.scaleBand replaces *ordinal*.rangeBands, *band*.bandwidth, *band*.align.
new d3.scalePoint replaces *ordinal*.rangePoints.
```js
varx=d3.scaleOrdinal()
.domain([0,1])
.range(["red","green","blue"])
.unknown(undefined);
x.domain();// [0, 1]
x(2);// undefined
x.domain();// [0, 1]
```
This is particularly useful for choropleths where you wish to use a color (such as light gray) for missing data.
d3.scaleOrdinal constructor now takes an optional *range*.
category scales now defined as arrays of colors for passing to d3.scaleOrdinal:
* d3.scale.category10 ↦ d3.schemeCategory10
...
...
@@ -733,6 +741,23 @@ category scales now defined as arrays of colors for passing to d3.scaleOrdinal:
* d3.scale.category20b ↦ d3.schemeCategory20b
* d3.scale.category20c ↦ d3.schemeCategory20c
new d3.scaleBand replaces *ordinal*.rangeBands, *band*.bandwidth, *band*.align.
new d3.scalePoint replaces *ordinal*.rangePoints.
[Sequential scales](https://github.com/d3/d3-scale#scaleSequential), are a new class of scales with a fixed output [interpolator](https://github.com/d3/d3-scale#sequential_interpolator) instead of a [range](https://github.com/d3/d3-scale#continuous_range). Typically these scales are used to implement continuous sequential or diverging color schemes. Inspired by Matplotlib’s new [perceptually-motived colormaps](https://bids.github.io/colormap/), 4.0 now features [viridis](https://github.com/d3/d3-scale#interpolateViridis), [inferno](https://github.com/d3/d3-scale#interpolateInferno), [magma](https://github.com/d3/d3-scale#interpolateMagma), [plasma](https://github.com/d3/d3-scale#interpolatePlasma) interpolators for use with sequential scales. Using [d3.quantize](https://github.com/d3/d3-interpolate#quantize), these interpolators can also be applied to [quantile](https://github.com/d3/d3-scale#quantile-scales), [quantize](https://github.com/d3/d3-scale#quantize-scales) and [threshold](https://github.com/d3/d3-scale#threshold-scales) scales.
4.0 also ships new Cubehelix schemes, including [Dave Green’s default](https://github.com/d3/d3-scale#interpolateCubehelixDefault) and a [cyclical rainbow](https://github.com/d3/d3-scale#interpolateRainbow) inspired by [Matteo Niccoli](https://mycarta.wordpress.com/2013/02/21/perceptual-rainbow-palette-the-method/):
