@@ -68,7 +68,7 @@ var i = d3.scan(data, function(a, b) { return a.value - b.value; }); // 2

data[i];// {name: "Carol", value: 1}

```

The new [d3.ticks](https://github.com/d3/d3-array#ticks) and [d3.tickStep](https://github.com/d3/d3-array#tickStep) methods are useful for generating human-readable numeric ticks. These methods are a low-level alternative to [*continuous*.ticks](https://github.com/d3/d3-scale#continuous_ticks), avoiding[d3-scale](https://github.com/d3/d3-scale)’s dependencies. The new implementation is also more accurate, returning the optimal number of ticks as measured by relative error.

The new [d3.ticks](https://github.com/d3/d3-array#ticks) and [d3.tickStep](https://github.com/d3/d3-array#tickStep) methods are useful for generating human-readable numeric ticks. These methods are a low-level alternative to [*continuous*.ticks](https://github.com/d3/d3-scale#continuous_ticks) from[d3-scale](https://github.com/d3/d3-scale). The new implementation is also more accurate, returning the optimal number of ticks as measured by relative error.

The [d3.range](https://github.com/d3/d3-array#range) method no longer makes an elaborate attempt to avoid floating-point error when *step* is not an integer. The returned values are strictly defined as *start* + *i*\**step*, where *i* is an integer. (Learn more about [floating point math](http://0.30000000000000004.com/).) d3.range returns the empty array for infinite ranges, rather than throwing an error.

The method signature for optional accessors has been changed to be more consistent with array methods such as [*array*.forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach): the accessor is passed the current element (*d*), the index (*i*), and the array (*array*), with *this* as undefined. This affects [d3.min](https://github.com/d3/d3-array#min), [d3.max](https://github.com/d3/d3-array#max), [d3.extent](https://github.com/d3/d3-array#extent), [d3.sum](https://github.com/d3/d3-array#sum), [d3.mean](https://github.com/d3/d3-array#mean), [d3.median](https://github.com/d3/d3-array#median), [d3.quantile](https://github.com/d3/d3-array#quantile), [d3.variance](https://github.com/d3/d3-array#variance) and [d3.deviation](https://github.com/d3/d3-array#deviation). The [d3.quantile](https://github.com/d3/d3-array#quantile) method previously did not take an accessor. Some methods with optional arguments now treat those arguments as missing if they are null or undefined, rather than strictly checking arguments.length.

The method signature for optional accessors has been changed to be more consistent with array methods such as [*array*.forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach): the accessor is passed the current element (*d*), the index (*i*), and the array (*data*), with *this* as undefined. This affects [d3.min](https://github.com/d3/d3-array#min), [d3.max](https://github.com/d3/d3-array#max), [d3.extent](https://github.com/d3/d3-array#extent), [d3.sum](https://github.com/d3/d3-array#sum), [d3.mean](https://github.com/d3/d3-array#mean), [d3.median](https://github.com/d3/d3-array#median), [d3.quantile](https://github.com/d3/d3-array#quantile), [d3.variance](https://github.com/d3/d3-array#variance) and [d3.deviation](https://github.com/d3/d3-array#deviation). The [d3.quantile](https://github.com/d3/d3-array#quantile) method previously did not take an accessor. Some methods with optional arguments now treat those arguments as missing if they are null or undefined, rather than strictly checking arguments.length.

### Histograms

The new [d3.histogram](https://github.com/d3/d3-array#histograms) API replaces d3.layout.histogram.

Rather than exposing *bin*.x and *bin*.dx on each returned bin, the histogram exposes *bin*.x0 and *bin*.x1, guaranteeing that *bin*.x0 is exactly equal to *bin*.x1 on the preceeding bin. The “frequency” and “probability” modes are no longer supported; each bin is simply an array of elements from the input data, so *bin*.length is equal to D3 3.x’s *bin*.y in frequency mode. To compute a probability distribution, divide the number of elements in each bin by the total number of elements.

The new [d3.histogram](https://github.com/d3/d3-array#histograms) API replaces d3.layout.histogram. Rather than exposing *bin*.x and *bin*.dx on each returned bin, the histogram exposes *bin*.x0 and *bin*.x1, guaranteeing that *bin*.x0 is exactly equal to *bin*.x1 on the preceeding bin. The “frequency” and “probability” modes are no longer supported; each bin is simply an array of elements from the input data, so *bin*.length is equal to D3 3.x’s *bin*.y in frequency mode. To compute a probability distribution, divide the number of elements in each bin by the total number of elements.

The *histogram*.range method has been renamed [*histogram*.domain](https://github.com/d3/d3-array#histogram_domain) for consistency with scales. The *histogram*.bins method has been renamed [*histogram*.thresholds](https://github.com/d3/d3-array#histogram_thresholds), and no longer accepts an upper value: *n* thresholds will produce *n* + 1 bins. If you specify a desired number of bins rather than thresholds, d3.histogram now uses [d3.ticks](https://github.com/d3/d3-array#ticks) to compute nice bin thresholds. In addition to the default Sturges’ formula, D3 now implements the [Freedman-Diaconis rule](https://github.com/d3/d3-array#thresholdFreedmanDiaconis) and [Scott’s normal reference rule](https://github.com/d3/d3-array#thresholdScott).

## Axes (d3-axis)

In place of d3.svg.axis and *axis*.orient, D3 4.0 now provides four constructors for each orientation: [d3.axisTop](https://github.com/d3/d3-axis#axisTop), [d3.axisRight](https://github.com/d3/d3-axis#axisRight), [d3.axisBottom](https://github.com/d3/d3-axis#axisBottom), [d3.axisLeft](https://github.com/d3/d3-axis#axisLeft). You can now pass a scale directly to the axis constructor.

To render axes in D3 3.x, you needed to not only instantiate the axis, but also style them:

To render axes properly in D3 3.x, you needed to style them:

D3 4.0 provides default styles and shorter syntax, so you can reduce all this to:

D3 4.0 provides default styles and shorter syntax. In place of d3.svg.axis and *axis*.orient, D3 4.0 now provides four constructors for each orientation: [d3.axisTop](https://github.com/d3/d3-axis#axisTop), [d3.axisRight](https://github.com/d3/d3-axis#axisRight), [d3.axisBottom](https://github.com/d3/d3-axis#axisBottom), [d3.axisLeft](https://github.com/d3/d3-axis#axisLeft). You can now pass a scale directly to the axis constructor. So you can reduce all of the above to: