links from Plot to the new D3 documentation (#1689)

Author: Fil

docs/features/curves.md

@@ -11,7 +11,7 @@ const numbers = d3.range(20).map(d3.randomLcg(42));
 
 # Curves
 
-A **curve** defines how to turn a discrete representation of a line as a sequence of points [[*x₀*, *y₀*], [*x₁*, *y₁*], [*x₂*, *y₂*], …] into a continuous path; *i.e.*, how to interpolate between points. Curves are used by the [line](../marks/line.md), [area](../marks/area.md), and [link](../marks/link.md) marks, and are implemented by [d3-shape](https://github.com/d3/d3-shape/blob/main/README.md#curves).
+A **curve** defines how to turn a discrete representation of a line as a sequence of points [[*x₀*, *y₀*], [*x₁*, *y₁*], [*x₂*, *y₂*], …] into a continuous path; *i.e.*, how to interpolate between points. Curves are used by the [line](../marks/line.md), [area](../marks/area.md), and [link](../marks/link.md) marks, and are implemented by [d3-shape](https://d3js.org/d3-shape/curve).
 
 <p>
   <label class="label-input">
@@ -81,6 +81,6 @@ The following named curve methods are supported:
 * *step-before* - a piecewise constant function where *x* changes after *y*
 * *auto* - like *linear*, but use the (possibly spherical) [projection](./projections.md), if any
 
-If **curve** is a function, it will be invoked with a given *context* in the same fashion as a [D3 curve factory](https://github.com/d3/d3-shape/blob/main/README.md#custom-curves). The *auto* curve is only available for the [line mark](../marks/line.md) and [link mark](../marks/link.md) and is typically used in conjunction with a spherical [projection](./projections.md) to interpolate along [geodesics](https://en.wikipedia.org/wiki/Geodesic).
+If **curve** is a function, it will be invoked with a given *context* in the same fashion as a [D3 curve factory](https://d3js.org/d3-shape/curve#custom-curves). The *auto* curve is only available for the [line mark](../marks/line.md) and [link mark](../marks/link.md) and is typically used in conjunction with a spherical [projection](./projections.md) to interpolate along [geodesics](https://en.wikipedia.org/wiki/Geodesic).
 
-The tension option only has an effect on bundle, cardinal and Catmull–Rom splines (*bundle*, *cardinal*, *cardinal-open*, *cardinal-closed*, *catmull-rom*, *catmull-rom-open*, and *catmull-rom-closed*). For bundle splines, it corresponds to [beta](https://github.com/d3/d3-shape/blob/main/README.md#curveBundle_beta); for cardinal splines, [tension](https://github.com/d3/d3-shape/blob/main/README.md#curveCardinal_tension); for Catmull–Rom splines, [alpha](https://github.com/d3/d3-shape/blob/main/README.md#curveCatmullRom_alpha).
+The tension option only has an effect on bundle, cardinal and Catmull–Rom splines (*bundle*, *cardinal*, *cardinal-open*, *cardinal-closed*, *catmull-rom*, *catmull-rom-open*, and *catmull-rom-closed*). For bundle splines, it corresponds to [beta](https://d3js.org/d3-shape/curve#curveBundle_beta); for cardinal splines, [tension](https://d3js.org/d3-shape/curve#curveCardinal_tension); for Catmull–Rom splines, [alpha](https://d3js.org/d3-shape/curve#curveCatmullRom_alpha).

docs/features/formats.md

@@ -7,7 +7,7 @@ import * as d3 from "d3";
 
 # Formats
 
-These helper functions are provided for convenience as a **tickFormat** option for the [axis mark](../marks/axis.md), as the **text** option for a [text mark](../marks/text.md), or other use. See also [d3-format](https://github.com/d3/d3-format), [d3-time-format](https://github.com/d3/d3-time-format), and JavaScript’s built-in [date formatting](https://observablehq.com/@mbostock/date-formatting) and [number formatting](https://observablehq.com/@mbostock/number-formatting).
+These helper functions are provided for convenience as a **tickFormat** option for the [axis mark](../marks/axis.md), as the **text** option for a [text mark](../marks/text.md), or other use. See also [d3-format](https://d3js.org/d3-format), [d3-time-format](https://d3js.org/d3-time-format), and JavaScript’s built-in [date formatting](https://observablehq.com/@mbostock/date-formatting) and [number formatting](https://observablehq.com/@mbostock/number-formatting).
 
 ## formatIsoDate(*date*)
 

docs/features/marks.md

@@ -433,7 +433,7 @@ sales = [
 Plot.dot(sales, {x: "units", y: "fruit"})
 ```
 
-While a column name such as `"units"` is the most concise way of specifying channel values, values can also be specified as functions for greater flexibility, say to transform data or derive a new column on the fly. Channel functions are invoked for each datum (*d*) in the data and return the corresponding channel value. (This is similar to how D3’s [*selection*.attr](https://github.com/d3/d3-selection/blob/main/README.md#selection_attr) accepts functions, though note that Plot channel functions should return abstract values, not visual values.)
+While a column name such as `"units"` is the most concise way of specifying channel values, values can also be specified as functions for greater flexibility, say to transform data or derive a new column on the fly. Channel functions are invoked for each datum (*d*) in the data and return the corresponding channel value. (This is similar to how D3’s [*selection*.attr](https://d3js.org/d3-selection/modifying#selection_attr) accepts functions, though note that Plot channel functions should return abstract values, not visual values.)
 
 ```js
 Plot.dot(sales, {x: (d) => d.units * 1000, y: (d) => d.fruit})

docs/features/plots.md

@@ -70,7 +70,7 @@ aapl = [
 ```
 
 :::tip
-Rather than baking data into JavaScript, use [JSON](https://en.wikipedia.org/wiki/JSON) or [CSV](https://en.wikipedia.org/wiki/Comma-separated_values) files to store data. You can use [d3.json](https://github.com/d3/d3-fetch/blob/main/README.md#json), [d3.csv](https://github.com/d3/d3-fetch/blob/main/README.md#csv), or [fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) to load a file. On Observable, you can also use a [file attachment](https://observablehq.com/@observablehq/file-attachments) or [SQL cell](https://observablehq.com/@observablehq/sql-cell).
+Rather than baking data into JavaScript, use [JSON](https://en.wikipedia.org/wiki/JSON) or [CSV](https://en.wikipedia.org/wiki/Comma-separated_values) files to store data. You can use [d3.json](https://d3js.org/d3-fetch#json), [d3.csv](https://d3js.org/d3-fetch#csv), or [fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) to load a file. On Observable, you can also use a [file attachment](https://observablehq.com/@observablehq/file-attachments) or [SQL cell](https://observablehq.com/@observablehq/sql-cell).
 :::
 
 To use data with Plot, pass the data as the first argument to the mark constructor. We can then assign columns of data such as *Date* and *Close* to visual properties of the mark (or “channels”) such as horizontal↔︎ position **x** and vertical↕︎ position **y**.

docs/features/projections.md

@@ -56,7 +56,7 @@ Plot.plot({
 
 Above, a [geo mark](../marks/geo.md) draws polygons representing land and a [sphere mark](../marks/geo.md#sphere-options) draws the outline of the globe. A [dot mark](../marks/dot.md) draws earthquakes as circles sized by magnitude.
 
-The geo mark is “projection aware” so that it can handle all the nuances of projecting spherical polygons to the screen—leaning on [d3-geo](https://github.com/d3/d3-geo) to provide [adaptive sampling](https://observablehq.com/@d3/adaptive-sampling) with configurable precision, [antimeridian cutting](https://observablehq.com/@d3/antimeridian-cutting), and clipping. The dot mark is not; instead, Plot applies the projection in place of the *x* and *y* scales. Hence, projections work with any mark that consumes continuous **x** and **y** channels—as well as marks that use **x1** & **y1** and **x2** & **y2**. Each mark implementation decides whether to handle projections specially or to treat the projection as any other position scale. (For example, the [line mark](../marks/line.md) is projection-aware to draw geodesics.)
+The geo mark is “projection aware” so that it can handle all the nuances of projecting spherical polygons to the screen—leaning on [d3-geo](https://d3js.org/d3-geo) to provide [adaptive sampling](https://observablehq.com/@d3/adaptive-sampling) with configurable precision, [antimeridian cutting](https://observablehq.com/@d3/antimeridian-cutting), and clipping. The dot mark is not; instead, Plot applies the projection in place of the *x* and *y* scales. Hence, projections work with any mark that consumes continuous **x** and **y** channels—as well as marks that use **x1** & **y1** and **x2** & **y2**. Each mark implementation decides whether to handle projections specially or to treat the projection as any other position scale. (For example, the [line mark](../marks/line.md) is projection-aware to draw geodesics.)
 
 :::info
 Marks that require *band* scales (bars, cells, and ticks) cannot be used with projections. Likewise one-dimensional marks such as rules cannot be used, though see [#1164](https://github.com/observablehq/plot/issues/1164).
@@ -131,7 +131,7 @@ Plot.plot({
 Use the *albers-usa* projection for U.S.-centric choropleth maps.
 :::
 
-For maps that focus on a specific region, use the **domain** option to zoom in. This object should be a GeoJSON object. For example, you can use [d3.geoCircle](https://github.com/d3/d3-geo/blob/main/README.md#geoCircle) to generate a circle of a given radius centered at a given longitude and latitude. You can also use the **inset** options for a bit of padding around the **domain**.
+For maps that focus on a specific region, use the **domain** option to zoom in. This object should be a GeoJSON object. For example, you can use [d3.geoCircle](https://d3js.org/d3-geo/shape#geoCircle) to generate a circle of a given radius centered at a given longitude and latitude. You can also use the **inset** options for a bit of padding around the **domain**.
 
 <p>
   <label class="label-input">
@@ -251,13 +251,13 @@ The following built-in named projections are supported:
 * *reflect-y* - like the identity projection, but *y* points up
 * null (default) - the null projection for pre-projected geometry in screen coordinates
 
-In addition to these named projections, the **projection** option may be specified as a [D3 projection](https://github.com/d3/d3-geo/blob/main/README.md#projections), or any custom projection that implements [*projection*.stream](https://github.com/d3/d3-geo/blob/main/README.md#projection_stream), or a function that receives a configuration object ({*width*, *height*, ...*options*}) and returns such a projection. In the last case, the width and height represent the frame dimensions minus any insets.
+In addition to these named projections, the **projection** option may be specified as a [D3 projection](https://d3js.org/d3-geo/projection), or any custom projection that implements [*projection*.stream](https://d3js.org/d3-geo/stream), or a function that receives a configuration object ({*width*, *height*, ...*options*}) and returns such a projection. In the last case, the width and height represent the frame dimensions minus any insets.
 
 If the **projection** option is specified as an object, the following additional projection options are supported:
 
 * **type** - one of the projection names above
-* **parallels** - the [standard parallels](https://github.com/d3/d3-geo/blob/main/README.md#conic_parallels) (for conic projections only)
-* **precision** - the [sampling threshold](https://github.com/d3/d3-geo/blob/main/README.md#projection_precision)
+* **parallels** - the [standard parallels](https://d3js.org/d3-geo/conic#conic_parallels) (for conic projections only)
+* **precision** - the [sampling threshold](https://d3js.org/d3-geo/projection#projection_precision)
 * **rotate** - a two- or three- element array of Euler angles to rotate the sphere
 * **domain** - a GeoJSON object to fit in the center of the (inset) frame
 * **inset** - inset by the given amount in pixels when fitting to the frame (default zero)

docs/features/scales.md

@@ -76,7 +76,7 @@ Plot.ruleX(gistemp, {x: "Date", stroke: "Anomaly"}).plot()
 ```
 :::
 
-While the resulting chart looks different, the *color* scale here behaves similarly to the `y` function above—the only difference is that it interpolates colors (using [d3.interpolateTurbo](https://github.com/d3/d3-scale-chromatic/blob/main/README.md#interpolateTurbo)) instead of numbers (the top and bottom sides of the plot frame):
+While the resulting chart looks different, the *color* scale here behaves similarly to the `y` function above—the only difference is that it interpolates colors (using [d3.interpolateTurbo](https://d3js.org/d3-scale-chromatic/sequential#interpolateTurbo)) instead of numbers (the top and bottom sides of the plot frame):
 
 ```js
 function color(anomaly) {
@@ -143,7 +143,7 @@ Plot.plot({x: {domain: [0, 100], reverse: true, grid: true}})
 
 If the domain is dates, Plot will default to a UTC scale. This is a linear scale with ticks based on the Gregorian calendar.
 
-<!-- Plot doesn’t parse dates; convert your strings to [Date](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date) instances with [d3.utcParse](https://github.com/d3/d3-time-format#utcParse) or [d3.autoType](https://github.com/d3/d3-dsv#autoType). -->
+<!-- Plot doesn’t parse dates; convert your strings to [Date](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date) instances with [d3.utcParse](https://d3js.org/d3-time-format#utcParse) or [d3.autoType](https://d3js.org/d3-dsv#autoType). -->
 
 :::plot https://observablehq.com/@observablehq/plot-continuous-scales
 ```js
@@ -179,7 +179,7 @@ Plot.plot({x: {type: "log", domain: [1e0, 1e5], grid: true}})
 ```
 :::
 
-If you prefer conventional notation, you can specify the **tickFormat** option to change the behavior of the axis. The **tickFormat** option can either be a [d3.format](https://github.com/d3/d3-format) string or a function that takes a tick value and returns the corresponding string. Note, however, that this may result in overlapping text.
+If you prefer conventional notation, you can specify the **tickFormat** option to change the behavior of the axis. The **tickFormat** option can either be a [d3.format](https://d3js.org/d3-format) string or a function that takes a tick value and returns the corresponding string. Note, however, that this may result in overlapping text.
 
 :::plot https://observablehq.com/@observablehq/plot-continuous-scales
 ```js
@@ -195,7 +195,7 @@ Plot.plot({x: {type: "log", base: 2, domain: [1e0, 1e4], ticks: 20, grid: true}}
 ```
 :::
 
-The domain of a log scale cannot include (or cross) zero; for this, consider a [bi-symmetric log](https://github.com/d3/d3-scale#symlog-scales) scale instead.
+The domain of a log scale cannot include (or cross) zero; for this, consider a [bi-symmetric log](https://d3js.org/d3-scale/symlog) scale instead.
 
 :::plot https://observablehq.com/@observablehq/plot-continuous-scales
 ```js
@@ -961,7 +961,7 @@ Top-level options are also supported as shorthand: **grid** (for *x* and *y* onl
 
 ## Sort mark option
 
-If an ordinal scale’s domain is not set, it defaults to natural ascending order; to order the domain by associated values in another dimension, either compute the domain manually (consider [d3.groupSort](https://github.com/d3/d3-array/blob/main/README.md#groupSort)) or use an associated mark’s **sort** option. For example, to sort bars by ascending frequency rather than alphabetically by letter:
+If an ordinal scale’s domain is not set, it defaults to natural ascending order; to order the domain by associated values in another dimension, either compute the domain manually (consider [d3.groupSort](https://d3js.org/d3-array/group#groupSort)) or use an associated mark’s **sort** option. For example, to sort bars by ascending frequency rather than alphabetically by letter:
 
 ```js
 Plot.barY(alphabet, {x: "letter", y: "frequency", sort: {x: "y"}})

docs/features/transforms.md

@@ -72,7 +72,7 @@ Plot.plot({
 
 Plot includes many useful transforms! For example, you can compute a [rolling average](../transforms/window.md) to smooth a noisy signal, [stack layers](../transforms/stack.md) for a streamgraph, or [dodge dots](../transforms/dodge.md) for a beeswarm. Plot’s various built-in transforms include: [bin](../transforms/bin.md), [centroid](../transforms/centroid.md), [dodge](../transforms/dodge.md), [filter](../transforms/filter.md), [group](../transforms/group.md), [hexbin](../transforms/hexbin.md), [interval](../transforms/interval.md), [map](../transforms/map.md), [normalize](../transforms/normalize.md), [reverse](../transforms/sort.md#reverse-options), [select](../transforms/select.md), [shuffle](../transforms/sort.md#shuffle-options), [sort](../transforms/sort.md), [stack](../transforms/stack.md), [tree](../transforms/tree.md), and [window](../transforms/window.md). If these don’t meet your needs, you can even implement a [custom transform](#custom-transforms).
 
-Transforms are never required—you can always aggregate and derive data yourself outside of Plot, and then pass in the binned values. For example, we could use [d3.bin](https://github.com/d3/d3-array/blob/main/README.md#bin) to compute a histogram of athletes’ weights as an array of {*x0*, *x1*, *length*} objects.
+Transforms are never required—you can always aggregate and derive data yourself outside of Plot, and then pass in the binned values. For example, we could use [d3.bin](https://d3js.org/d3-array/bin) to compute a histogram of athletes’ weights as an array of {*x0*, *x1*, *length*} objects.
 
 ```js
 bins = d3.bin().thresholds(80).value((d) => d.weight)(olympians)

docs/marks/area.md

@@ -290,7 +290,7 @@ The **stroke** defaults to *none*. The **fill** defaults to *currentColor* if th
 
 Points along the baseline and topline are connected in input order. Likewise, if there are multiple series via the **z**, **fill**, or **stroke** channel, the series are drawn in input order such that the last series is drawn on top. Typically, the data is already in sorted order, such as chronological for time series; if sorting is needed, consider a [sort transform](../transforms/sort.md).
 
-The area mark supports [curve options](../features/curves.md) to control interpolation between points. If any of the **x1**, **y1**, **x2**, or **y2** values are invalid (undefined, null, or NaN), the baseline and topline will be interrupted, resulting in a break that divides the area shape into multiple segments. (See [d3-shape’s *area*.defined](https://github.com/d3/d3-shape/blob/main/README.md#area_defined) for more.) If an area segment consists of only a single point, it may appear invisible unless rendered with rounded or square line caps. In addition, some curves such as *cardinal-open* only render a visible segment if it contains multiple points.
+The area mark supports [curve options](../features/curves.md) to control interpolation between points. If any of the **x1**, **y1**, **x2**, or **y2** values are invalid (undefined, null, or NaN), the baseline and topline will be interrupted, resulting in a break that divides the area shape into multiple segments. (See [d3-shape’s *area*.defined](https://d3js.org/d3-shape/area#area_defined) for more.) If an area segment consists of only a single point, it may appear invisible unless rendered with rounded or square line caps. In addition, some curves such as *cardinal-open* only render a visible segment if it contains multiple points.
 
 ## areaY(*data*, *options*)