diff --git a/README.md b/README.md index 8a224d6f..f5bab104 100644 --- a/README.md +++ b/README.md @@ -505,7 +505,7 @@ Returns the difference between adjacent tick values if the same arguments were p # d3.range([start, ]stop[, step]) · [Source](https://github.com/d3/d3-array/blob/master/src/range.js), [Examples](https://observablehq.com/@d3/d3-range) -Returns an array containing an arithmetic progression, similar to the Python built-in [range](http://docs.python.org/library/functions.html#range). This method is often used to iterate over a sequence of uniformly-spaced numeric values, such as the indexes of an array or the ticks of a linear scale. (See also [d3.ticks](#ticks) for nicely-rounded values.) +Returns an array containing an arithmetic progression, similar to the Python built-in [range](http://docs.python.org/library/functions.html#range). This method is often used to iterate over a sequence of uniformly-spaced numeric values, such as the indexes of an array or the ticks of a linear scale. (See also [d3.ticks](#ticks) for nicely-rounded values, and [d3.linspace](#linspace) if you prefer to specify the number of values rather than the step.) If *step* is omitted, it defaults to 1. If *start* is omitted, it defaults to 0. The *stop* value is exclusive; it is not included in the result. If *step* is positive, the last element is the largest *start* + *i* \* *step* less than *stop*; if *step* is negative, the last element is the smallest *start* + *i* \* *step* greater than *stop*. If the returned array would contain an infinite number of values, an empty range is returned. @@ -524,6 +524,15 @@ d3.range(0, 1, 1 / 49); // BAD: returns 50 elements! d3.range(49).map(function(d) { return d / 49; }); // GOOD: returns 49 elements. ``` +# d3.linspace(start, stop[, n][, endpoint]) · [Source](https://github.com/d3/d3-array/blob/master/src/linspace.js) + +Returns an array containing an arithmetic progression of *n* values ranging from *start* to *end*, including *end* if *endpoint* is requested. Similar to numpy’s [linspace](https://numpy.org/doc/stable/reference/generated/numpy.linspace.html). Defaults to *n* = 50 and *endpoint* = true. + +```js +d3.linspace(0, 1, 101); // [0, 0.01, 0.02, …, 0.99, 1] +d3.linspace(1, 0, 10, false); // [1, 0.9, 0.8, …, 0.1] +``` + # d3.transpose(matrix) · [Source](https://github.com/d3/d3-array/blob/master/src/transpose.js), [Examples](https://observablehq.com/@d3/d3-transpose) Uses the [zip](#zip) operator as a two-dimensional [matrix transpose](http://en.wikipedia.org/wiki/Transpose). diff --git a/test/linspace-test.js b/test/linspace-test.js index 41492cd0..8442658c 100644 --- a/test/linspace-test.js +++ b/test/linspace-test.js @@ -1,7 +1,7 @@ var tape = require("tape"), arrays = require("../"); -tape.only("linspace(start, stop)", function(test) { +tape("linspace(start, stop)", function(test) { test.deepEqual(arrays.linspace(0, 49), [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, @@ -21,3 +21,9 @@ tape("linspace(start, stop, n, false)", function(test) { test.deepEqual(arrays.linspace(2, 3, 5, false), [2, 2.2, 2.4, 2.6, 2.8]); test.end(); }); + +tape("linspace(start, stop, n) descending", function(test) { + test.deepEqual(arrays.linspace(5, 1, 5), [5, 4, 3, 2, 1]); + test.deepEqual(arrays.linspace(5, 0, 5, false), [5, 4, 3, 2, 1]); + test.end(); +});