Update README

Author: mbostock

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## 0.2.3
 
-*Not yet released.* These notes are a work in progress.
+Released September 24, 2021.
 
 Rect, bar, and rule marks now accept an *interval* option that allows to derive *x1* and *x2* from *x*, or *y1* and *y2* from *y*, where appropriate. A typical use case is for data that represents a fixed time interval; for example, using d3.utcDay as the interval creates rects that span a whole day, from UTC midnight to UTC midnight, that contains the associated time instant. The interval must be specifed as an object with two methods: **floor**(*x*) returns the start of the interval *x1* for the given *x*, while **offset**(*x*) returns the end of the interval *x2* for the given interval start *x*. If the interval is specified as a number, *x1* and *x2* are taken as the two consecutive multiples of *n* that bracket *x*.
 

README.md

@@ -610,6 +610,8 @@ Returns a new horizontal bar↔︎ with the given *data* and *options*. The foll
 
 If neither the **x1** nor **x2** option is specified, the **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxstack-options); this is the typical configuration for a horizontal bar chart with bars aligned at *x* = 0. If the **x** option is not specified, it defaults to the identity function.
 
+If an **interval** is specified, such as d3.utcDay, **x1** and **x2** can be derived from **x**: *interval*.floor(*x*) is invoked for each *x* to produce *x1*, and *interval*.offset(*x1*) is invoked for each *x1* to produce *x2*. If the interval is specified as a number *n*, *x1* and *x2* are taken as the two consecutive multiples of *n* that bracket *x*.
+
 In addition to the [standard bar channels](#bar), the following optional channels are supported:
 
 * **y** - the vertical position; bound to the *y* scale, which must be *band*
@@ -629,6 +631,8 @@ Returns a new vertical bar↕︎ with the given *data* and *options*. The follow
 
 If neither the **y1** nor **y2** option is specified, the **y** option may be specified as shorthand to apply an implicit [stackY transform](#plotstackystack-options); this is the typical configuration for a vertical bar chart with bars aligned at *y* = 0. If the **y** option is not specified, it defaults to the identity function.
 
+If an **interval** is specified, such as d3.utcDay, **y1** and **y2** can be derived from **y**: *interval*.floor(*y*) is invoked for each *y* to produce *y1*, and *interval*.offset(*y1*) is invoked for each *y1* to produce *y2*. If the interval is specified as a number *n*, *y1* and *y2* are taken as the two consecutive multiples of *n* that bracket *y*.
+
 In addition to the [standard bar channels](#bar), the following optional channels are supported:
 
 * **x** - the horizontal position; bound to the *x* scale, which must be *band*
@@ -801,7 +805,9 @@ The following channels are optional:
 * **x2** - the ending horizontal position; bound to the *x* scale
 * **y2** - the ending vertical position; bound to the *y* scale
 
-Typically either **x1** and **x2** are specified, or **y1** and **y2**, or both. **x1** and **x2** can be derived from **x** and an **interval** object (such as d3.utcDay) with a **floor** method that returns *x1* from *x* and an **offset** method that returns *x2* from *x1*. If the interval is specified as a number *n*, *x1* and *x2* are taken as the two consecutive multiples of *n* that bracket *x*. The interval may be specified either as as {x, interval} or x: {value, interval}—typically to apply different intervals to x and y.
+Typically either **x1** and **x2** are specified, or **y1** and **y2**, or both.
+
+If an **interval** is specified, such as d3.utcDay, **x1** and **x2** can be derived from **x**: *interval*.floor(*x*) is invoked for each *x* to produce *x1*, and *interval*.offset(*x1*) is invoked for each *x1* to produce *x2*. The same is true for *y*, *y1*, and *y2*, respectively. If the interval is specified as a number *n*, *x1* and *x2* are taken as the two consecutive multiples of *n* that bracket *x*. The interval may be specified either as as {x, interval} or x: {value, interval}—typically to apply different intervals to x and y.
 
 The rect mark supports the [standard mark options](#marks), including insets and rounded corners. The **stroke** defaults to none. The **fill** defaults to currentColor if the stroke is none, and to none otherwise.
 
@@ -854,6 +860,8 @@ Returns a new rule↕︎ with the given *data* and *options*. In addition to the
 
 If the **x** option is not specified, it defaults to the identity function and assumes that *data* = [*x₀*, *x₁*, *x₂*, …]. If a **y** option is specified, it is shorthand for the **y2** option with **y1** equal to zero; this is the typical configuration for a vertical lollipop chart with rules aligned at *y* = 0. If the **y1** channel is not specified, the rule will start at the top of the plot (or facet). If the **y2** channel is not specified, the rule will end at the bottom of the plot (or facet).
 
+If an **interval** is specified, such as d3.utcDay, **y1** and **y2** can be derived from **y**: *interval*.floor(*y*) is invoked for each *y* to produce *y1*, and *interval*.offset(*y1*) is invoked for each *y1* to produce *y2*. If the interval is specified as a number *n*, *y1* and *y2* are taken as the two consecutive multiples of *n* that bracket *y*.
+
 #### Plot.ruleY(*data*, *options*)
 
 ```js
@@ -871,6 +879,8 @@ Returns a new rule↔︎ with the given *data* and *options*. In addition to the
 
 If the **y** option is not specified, it defaults to the identity function and assumes that *data* = [*y₀*, *y₁*, *y₂*, …]. If the **x** option is specified, it is shorthand for the **x2** option with **x1** equal to zero; this is the typical configuration for a horizontal lollipop chart with rules aligned at *x* = 0. If the **x1** channel is not specified, the rule will start at the left edge of the plot (or facet). If the **x2** channel is not specified, the rule will end at the right edge of the plot (or facet).
 
+If an **interval** is specified, such as d3.utcDay, **x1** and **x2** can be derived from **x**: *interval*.floor(*x*) is invoked for each *x* to produce *x1*, and *interval*.offset(*x1*) is invoked for each *x1* to produce *x2*. If the interval is specified as a number *n*, *x1* and *x2* are taken as the two consecutive multiples of *n* that bracket *x*.
+
 ### Text
 
 [<img src="./img/text.png" width="320" height="198" alt="a bar chart with text labels">](https://observablehq.com/@observablehq/plot-text)