Update README

Author: mbostock

README.md

@@ -512,7 +512,7 @@ Returns a new area with the given *data* and *options*. Plot.area is rarely used
 Plot.areaX(aapl, {y: "Date", x: "Close"})
 ```
 
-Returns a new area with the given *data* and *options*. This constructor is used when the baseline and topline share *y* values, as in a time-series area chart where time goes up↑. If neither the **x1** nor **x2** option is specified, a **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxoptions); this is the typical configuration for an area chart with a baseline at *x* = 0. If the **x** option is not specified, it defaults to the identity function. The **y** option specifies the **y1** channel; and the **y1** and **y2** options are ignored.
+Returns a new area with the given *data* and *options*. This constructor is used when the baseline and topline share *y* values, as in a time-series area chart where time goes up↑. If neither the **x1** nor **x2** option is specified, the **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxoptions); this is the typical configuration for an area chart with a baseline at *x* = 0. If the **x** option is not specified, it defaults to the identity function. The **y** option specifies the **y1** channel; and the **y1** and **y2** options are ignored.
 
 #### Plot.areaY(*data*, *options*)
 
@@ -541,7 +541,7 @@ Returns a new horizontal bar↔︎ with the given *data* and *options*. The foll
 * **x1** - the starting horizontal position; bound to the *x* scale
 * **x2** - the ending horizontal position; bound to the *x* scale
 
-If neither the **x1** nor **x2** option is specified, a **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxoptions); 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 neither the **x1** nor **x2** option is specified, the **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxoptions); 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.
 
 In addition to the [standard bar channels](#bar), the following optional channels are supported:
 
@@ -750,15 +750,15 @@ Returns a new rect with the given *data* and *options*.
 Plot.rectX(athletes, Plot.binY({x: "count"}, {y: "weight"}))
 ```
 
-Equivalent to [Plot.rect](#plotrectdata-options), except that if the *x* option is specified, it corresponds to the *x2* channel while the *x1* channel defaults to zero. This constructor is typically used for vertically-oriented histograms (*e.g.*, where bins extend right→).
+Equivalent to [Plot.rect](#plotrectdata-options), except that if neither the **x1** nor **x2** option is specified, the **x** option may be specified as shorthand to apply an implicit [stackX transform](#plotstackxoptions); this is the typical configuration for a histogram with rects aligned at *x* = 0. If the **x** option is not specified, it defaults to the identity function.
 
 #### Plot.rectY(*data*, *options*)
 
 ```js
 Plot.rectY(athletes, Plot.binX({y: "count"}, {x: "weight"}))
 ```
 
-Equivalent to [Plot.rect](#plotrectdata-options), except that the *x* option specifies the *x1* channel, and if the *y* option is specified, it corresponds to the *y2* channel while the *y1* channel defaults to zero. This constructor is typically used for horizontally-oriented histograms (*e.g.*, where bins extend up↑).
+Equivalent to [Plot.rect](#plotrectdata-options), except that if neither the **y1** nor **y2** option is specified, a **y** option may be specified as shorthand to apply an implicit [stackY transform](#plotstackyoptions); this is the typical configuration for a histogram with rects aligned at *y* = 0. If the **y** option is not specified, it defaults to the identity function.
 
 ### Rule
 
@@ -800,7 +800,7 @@ Returns a new rule↔︎ with the given *data* and *options*. In addition to the
 * **x1** - the starting horizontal position; bound to the *x* scale
 * **x2** - the ending horizontal position; bound to the *x* scale
 
-If the **y** option is not specified, it defaults to the identity function and assumes that *data* = [*y₀*, *y₁*, *y₂*, …]. If a **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 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).
 
 ### Text