Implement Binary prefix, Currency prefix (Merge #70 #81)

README.md

@@ -133,9 +133,9 @@ The *symbol* can be:
 
 The *zero* (`0`) option enables zero-padding; this implicitly sets *fill* to `0` and *align* to `=`. The *width* defines the minimum field width; if not specified, then the width will be determined by the content. The *comma* (`,`) option enables the use of a group separator, such as a comma for thousands.
 
-Depending on the *type*, the *precision* either indicates the number of digits that follow the decimal point (types `f` and `%`), or the number of significant digits (types `​`, `e`, `g`, `r`, `s` and `p`). If the precision is not specified, it defaults to 6 for all types except `​` (none), which defaults to 12. Precision is ignored for integer formats (types `b`, `o`, `d`, `x`, `X` and `c`). See [precisionFixed](#precisionFixed) and [precisionRound](#precisionRound) for help picking an appropriate precision.
+Depending on the *type*, the *precision* either indicates the number of digits that follow the decimal point (types `f` and `%`), or the number of significant digits (types `​`, `e`, `g`, `K`, `r`, `s` and `p`). If the precision is not specified, it defaults to 6 for all types except `​` (none), which defaults to 12. Precision is ignored for integer formats (types `b`, `o`, `d`, `x`, `X` and `c`). See [precisionFixed](#precisionFixed) and [precisionRound](#precisionRound) for help picking an appropriate precision.
 
-The `~` option trims insignificant trailing zeros across all format types. This is most commonly used in conjunction with types `r`, `e`, `s` and `%`. For example:
+The `~` option trims insignificant trailing zeros across all format types. This is most commonly used in conjunction with types `r`, `e`, `s`, `K` and `%`. For example:
 
 ```js
 d3.format("s")(1500);  // "1.50000k"
@@ -149,6 +149,7 @@ The available *type* values are:
 * `g` - either decimal or exponent notation, rounded to significant digits.
 * `r` - decimal notation, rounded to significant digits.
 * `s` - decimal notation with an [SI prefix](#locale_formatPrefix), rounded to significant digits.
+* `K` - decimal notation with a [currency prefix](#locale_formatCurrencyPrefix), rounded to significant digits.
 * `%` - multiply by 100, and then decimal notation with a percent sign.
 * `p` - multiply by 100, round to significant digits, and then decimal notation with a percent sign.
 * `b` - binary notation, rounded to integer.
@@ -167,7 +168,7 @@ d3.format(".1")(42);  // "4e+1"
 d3.format(".1")(4.2); // "4"
 ```
 
-<a name="locale_formatPrefix" href="#locale_formatPrefix">#</a> <i>locale</i>.<b>formatPrefix</b>(<i>specifier</i>, <i>value</i>) [<>](https://github.com/d3/d3-format/blob/master/src/locale.js#L127 "Source")
+<a name="locale_formatPrefix" href="#locale_formatPrefix">#</a> <i>locale</i>.<b>formatPrefix</b>(<i>specifier</i>, <i>value</i>) [<>](https://github.com/d3/d3-format/blob/master/src/locale.js#L152 "Source")
 
 Equivalent to [*locale*.format](#locale_format), except the returned function will convert values to the units of the appropriate [SI prefix](https://en.wikipedia.org/wiki/Metric_prefix#List_of_SI_prefixes) for the specified numeric reference *value* before formatting in fixed point notation. The following prefixes are supported:
 
@@ -199,6 +200,16 @@ f(0.0042); // "4,200µ"
 
 This method is useful when formatting multiple numbers in the same units for easy comparison. See [precisionPrefix](#precisionPrefix) for help picking an appropriate precision, and [bl.ocks.org/9764126](http://bl.ocks.org/mbostock/9764126) for an example.
 
+<a name="locale_formatCurrencyPrefix" href="#locale_formatCurrencyPrefix">#</a> <i>locale</i>.<b>formatCurrencyPrefix</b>(<i>specifier</i>, <i>value</i>) [<>](https://github.com/d3/d3-format/blob/master/src/locale.js#L153 "Source")
+
+Equivalent to [*locale*.locale_formatPrefix](#locale_formatPrefix), except it uses common currency abbreviations:
+
+* `​` (none) - 10⁰
+* `K` - thousands, 10³
+* `M` - millions, 10⁶
+* `B` - billions, 10⁹
+* `T` - trillions, 10¹²
+
 <a name="formatSpecifier" href="#formatSpecifier">#</a> d3.<b>formatSpecifier</b>(<i>specifier</i>) [<>](https://github.com/d3/d3-format/blob/master/src/formatSpecifier.js "Source")
 
 Parses the specified *specifier*, returning an object with exposed fields that correspond to the [format specification mini-language](#locale_format) and a toString method that reconstructs the specifier. For example, `formatSpecifier("s")` returns:
@@ -290,6 +301,10 @@ f(1.2e6); // "1.2M"
 f(1.3e6); // "1.3M"
 ```
 
+<a name="currencyPrecisionPrefix" href="#currencyPrecisionPrefix">#</a> d3.<b>currencyPrecisionPrefix</b>(<i>step</i>, <i>value</i>) [<>](https://github.com/d3/d3-format/blob/master/src/currencyPrecisionPrefix.js "Source")
+
+Returns a suggested decimal precision for use with [*locale*.formatCurrencyPrefix](#locale_formatCurrencyPrefix) given the specified numeric *step* and reference *value*. This is the equivalent of [*locale*.precisionPrefix](#locale_precisionPrefix) using common currency abbreviations instead of SI prefixes.
+
 <a name="precisionRound" href="#precisionRound">#</a> d3.<b>precisionRound</b>(<i>step</i>, <i>max</i>) [<>](https://github.com/d3/d3-format/blob/master/src/precisionRound.js "Source")
 
 Returns a suggested decimal precision for format types that round to significant digits given the specified numeric *step* and *max* values. The *step* represents the minimum absolute difference between values that will be formatted, and the *max* represents the largest absolute value that will be formatted. (This assumes that the values to be formatted are also multiples of *step*.) For example, given the numbers 0.99, 1.0, and 1.01, the *step* should be 0.01, the *max* should be 1.01, and the suggested precision is 3:
@@ -331,6 +346,7 @@ Returns a *locale* object for the specified *definition* with [*locale*.format](
 * `thousands` - the group separator (e.g., `","`).
 * `grouping` - the array of group sizes (e.g., `[3]`), cycled as needed.
 * `currency` - the currency prefix and suffix (e.g., `["$", ""]`).
+* `currencyAbbreviations` - the list of abbreviated suffixes for currency values; an array of elements for each: units, thousands, millions, billions and trillions; defaults to `["", "K", "M", "B", "T"]`. The number of elements can vary.
 * `numerals` - optional; an array of ten strings to replace the numerals 0-9.
 * `percent` - optional; the percent sign (defaults to `"%"`).
 * `minus` - optional; the minus sign (defaults to hyphen-minus, `"-"`).

locale/de-DE.json

@@ -2,5 +2,6 @@
   "decimal": ",",
   "thousands": ".",
   "grouping": [3],
-  "currency": ["", "\u00a0€"]
+  "currency": ["", "\u00a0€"],
+  "currencyAbbreviations": ["", "", "\u00a0Mio.", "\u00a0Mrd.", "\u00a0Bio."]
 }

locale/en-GB.json

@@ -2,5 +2,6 @@
   "decimal": ".",
   "thousands": ",",
   "grouping": [3],
-  "currency": ["£", ""]
+  "currency": ["£", ""],
+  "currencyAbbreviations": ["", "k", "m", "bn", "tn"]
 }

locale/en-US.json

@@ -2,5 +2,6 @@
   "decimal": ".",
   "thousands": ",",
   "grouping": [3],
-  "currency": ["$", ""]
+  "currency": ["$", ""],
+  "currencyAbbreviations": ["", "K", "M", "B", "T"]
 }

locale/es-ES.json

@@ -2,5 +2,6 @@
   "decimal": ",",
   "thousands": ".",
   "grouping": [3],
-  "currency": ["", "\u00a0€"]
+  "currency": ["", "\u00a0€"],
+  "currencyAbbreviations": ["", "\u00a0mil", "\u00a0M", "\u00a0mil M", "\u00a0B"]
 }

locale/fr-FR.json

@@ -3,5 +3,6 @@
   "thousands": "\u00a0",
   "grouping": [3],
   "currency": ["", "\u00a0€"],
-  "percent": "\u202f%"
+  "percent": "\u202f%",
+  "currencyAbbreviations": ["", "\u00a0k", "\u00a0M", "\u00a0Md", "\u00a0Bn"]
 }

locale/it-IT.json

@@ -2,5 +2,6 @@
   "decimal": ",",
   "thousands": ".",
   "grouping": [3],
-  "currency": ["€", ""]
+  "currency": ["€", ""],
+  "currencyAbbreviations": ["", "", "\u00a0Mio", "\u00a0Mrd", "\u00a0Bln"]
 }

locale/nl-NL.json

@@ -2,5 +2,6 @@
   "decimal": ",",
   "thousands": ".",
   "grouping": [3],
-  "currency": ["€\u00a0", ""]
+  "currency": ["€\u00a0", ""],
+  "currencyAbbreviations": ["", "K", "\u00a0mln.", "\u00a0mld.", "\u00a0bln."]
 }

src/currencyPrecisionPrefix.js

@@ -0,0 +1,3 @@
+import { createPrecisionPrefix } from "./precisionPrefix.js";
+
+export default createPrecisionPrefix(0, 4);

src/defaultLocale.js

@@ -2,6 +2,7 @@ import formatLocale from "./locale.js";
 
 var locale;
 export var format;
+export var formatCurrencyPrefix;
 export var formatPrefix;
 
 defaultLocale({
@@ -15,6 +16,7 @@ defaultLocale({
 export default function defaultLocale(definition) {
   locale = formatLocale(definition);
   format = locale.format;
+  formatCurrencyPrefix = locale.formatCurrencyPrefix;
   formatPrefix = locale.formatPrefix;
   return locale;
 }

src/formatBinaryPrefixAuto.js

@@ -0,0 +1,46 @@
+export var binaryPrefixExponent;
+
+export default function(x, p) {
+  var binaryExponent = 0;
+  if (x === Infinity) return binaryPrefixExponent = 0, x;
+
+  while (Math.round(x) >= 1024 && binaryExponent < 80) {
+    binaryExponent += 10;
+    x /= 1024;
+  }
+
+  if (p <= 3 && Math.round(x) >= 1000) {
+    // Unlike SI prefixes, integers can take three digits.
+    binaryExponent += 10;
+    x /= 1024;
+  }
+
+  binaryPrefixExponent = Math.max(0, Math.min(8, Math.floor(binaryExponent / 10))) * 10;
+  var i = binaryExponent - binaryPrefixExponent + 1,
+      coefficient = x * i,
+      split = ('' + coefficient).split('.'),
+      integer = split[0],
+      fraction = split[1] || '',
+      n = (integer + fraction).length;
+
+  if (n === p) return coefficient;
+
+  if (n > p) {
+    var fractionLength = Math.max(0, p - integer.length);
+
+    while (+coefficient.toFixed(fractionLength) === 0) {
+      fractionLength += 1;
+    }
+
+    coefficient = coefficient.toFixed(fractionLength);
+  } else {
+    coefficient = integer + '.' + fraction;
+
+    while (n < p) {
+      coefficient += '0';
+      n += 1;
+    }
+  }
+
+  return coefficient;
+}

src/formatPrefixAuto.js

@@ -2,15 +2,25 @@ import formatDecimal from "./formatDecimal.js";
 
 export var prefixExponent;
 
-export default function(x, p) {
+function formatSignificantDigitsForPrefixes(x, p, minPrefixOrder, maxPrefixOrder) {
   var d = formatDecimal(x, p);
   if (!d) return x + "";
   var coefficient = d[0],
       exponent = d[1],
-      i = exponent - (prefixExponent = Math.max(-8, Math.min(8, Math.floor(exponent / 3))) * 3) + 1,
+      i = exponent - (prefixExponent = Math.max(minPrefixOrder, Math.min(maxPrefixOrder, Math.floor(exponent / 3))) * 3) + 1,
       n = coefficient.length;
   return i === n ? coefficient
       : i > n ? coefficient + new Array(i - n + 1).join("0")
       : i > 0 ? coefficient.slice(0, i) + "." + coefficient.slice(i)
-      : "0." + new Array(1 - i).join("0") + formatDecimal(x, Math.max(0, p + i - 1))[0]; // less than 1y!
+      : "0." + new Array(1 - i).join("0") + formatDecimal(x, Math.max(0, p + i - 1))[0]; // less than the smallest prefix
+}
+
+export function createFormatCurrencyPrefixAutoForLocale(currencyAbbreviations) {
+  return function formatCurrencyPrefixAuto(x, p) {
+    return formatSignificantDigitsForPrefixes(x, p, 0, currencyAbbreviations.length - 1);
+  }
+}
+
+export default function(x, p) {
+  return formatSignificantDigitsForPrefixes(x, p, -8, 8);
 }

src/formatTypes.js

@@ -1,14 +1,17 @@
-import formatPrefixAuto from "./formatPrefixAuto.js";
+import formatBinaryPrefixAuto from "./formatBinaryPrefixAuto.js";
+import formatPrefixAuto, { createFormatCurrencyPrefixAutoForLocale } from "./formatPrefixAuto.js";
 import formatRounded from "./formatRounded.js";
 
 export default {
   "%": function(x, p) { return (x * 100).toFixed(p); },
+  "B": formatBinaryPrefixAuto,
   "b": function(x) { return Math.round(x).toString(2); },
   "c": function(x) { return x + ""; },
   "d": function(x) { return Math.round(x).toString(10); },
   "e": function(x, p) { return x.toExponential(p); },
   "f": function(x, p) { return x.toFixed(p); },
   "g": function(x, p) { return x.toPrecision(p); },
+  "K": createFormatCurrencyPrefixAutoForLocale, // depends of the current locale
   "o": function(x) { return Math.round(x).toString(8); },
   "p": function(x, p) { return formatRounded(x * 100, p); },
   "r": formatRounded,

src/index.js

@@ -1,4 +1,5 @@
-export {default as formatDefaultLocale, format, formatPrefix} from "./defaultLocale.js";
+export {default as currencyPrecisionPrefix} from "./currencyPrecisionPrefix.js";
+export {default as formatDefaultLocale, format, formatCurrencyPrefix, formatPrefix} from "./defaultLocale.js";
 export {default as formatLocale} from "./locale.js";
 export {default as formatSpecifier, FormatSpecifier} from "./formatSpecifier.js";
 export {default as precisionFixed} from "./precisionFixed.js";

src/locale.js

@@ -5,13 +5,17 @@ import formatSpecifier from "./formatSpecifier.js";
 import formatTrim from "./formatTrim.js";
 import formatTypes from "./formatTypes.js";
 import {prefixExponent} from "./formatPrefixAuto.js";
+import {binaryPrefixExponent} from "./formatBinaryPrefixAuto.js";
 import identity from "./identity.js";
 
 var map = Array.prototype.map,
-    prefixes = ["y","z","a","f","p","n","µ","m","","k","M","G","T","P","E","Z","Y"];
+    SIprefixes = ["y","z","a","f","p","n","µ","m","","k","M","G","T","P","E","Z","Y"],
+    defaultCurrencyAbbreviations = ["", "K", "M", "B", "T"],
+    binaryPrefixes = ["", "Ki","Mi","Gi","Ti","Pi","Ei","Zi","Yi"];
 
 export default function(locale) {
   var group = locale.grouping === undefined || locale.thousands === undefined ? identity : formatGroup(map.call(locale.grouping, Number), locale.thousands + ""),
+      currencyAbbreviations = locale.currencyAbbreviations === undefined ? defaultCurrencyAbbreviations : locale.currencyAbbreviations,
       currencyPrefix = locale.currency === undefined ? "" : locale.currency[0] + "",
       currencySuffix = locale.currency === undefined ? "" : locale.currency[1] + "",
       decimal = locale.decimal === undefined ? "." : locale.decimal + "",
@@ -52,14 +56,18 @@ export default function(locale) {
     // Is this an integer type?
     // Can this type generate exponential notation?
     var formatType = formatTypes[type],
-        maybeSuffix = /[defgprs%]/.test(type);
+        maybeSuffix = /[BdefgKprs%]/.test(type);
+
+    if (type === 'K')
+      formatType = formatType(currencyAbbreviations);
 
     // Set the default precision if not specified,
     // or clamp the specified precision to the supported range.
     // For significant precision, it must be in [1, 21].
     // For fixed precision, it must be in [0, 20].
-    precision = precision === undefined ? 6
-        : /[gprs]/.test(type) ? Math.max(1, Math.min(21, precision))
+    // For financial type, default precision is 3 significant digits instead of 6.
+    precision = precision === undefined ? (type === "K" ? 3 : 6)
+        : /[BgKprs]/.test(type) ? Math.max(1, Math.min(21, precision))
         : Math.max(0, Math.min(20, precision));
 
     function format(value) {
@@ -87,7 +95,12 @@ export default function(locale) {
 
         // Compute the prefix and suffix.
         valuePrefix = (valueNegative ? (sign === "(" ? sign : minus) : sign === "-" || sign === "(" ? "" : sign) + valuePrefix;
-        valueSuffix = (type === "s" ? prefixes[8 + prefixExponent / 3] : "") + valueSuffix + (valueNegative && sign === "(" ? ")" : "");
+        switch (type) {
+          case "s": valueSuffix = SIprefixes[8 + prefixExponent / 3] + valueSuffix; break;
+          case "K": valueSuffix = currencyAbbreviations[prefixExponent / 3] + valueSuffix; break;
+          case "B": valueSuffix = binaryPrefixes[binaryPrefixExponent / 10] + valueSuffix; break;
+        }
+        valueSuffix += valueNegative && sign === "(" ? ")" : "";
 
         // Break the formatted value into the integer “value” part that can be
         // grouped, and fractional or exponential “suffix” part that is not.
@@ -131,18 +144,24 @@ export default function(locale) {
     return format;
   }
 
-  function formatPrefix(specifier, value) {
-    var f = newFormat((specifier = formatSpecifier(specifier), specifier.type = "f", specifier)),
-        e = Math.max(-8, Math.min(8, Math.floor(exponent(value) / 3))) * 3,
+  function createFormatPrefix(prefixes, minimumPrefixOrder, maximumPrefixOrder) {
+    return function(specifier, value) {
+      var f = newFormat((specifier = formatSpecifier(specifier), specifier.type = "f", specifier)),
+        e = Math.max(minimumPrefixOrder, Math.min(maximumPrefixOrder, Math.floor(exponent(value) / 3))) * 3,
         k = Math.pow(10, -e),
-        prefix = prefixes[8 + e / 3];
-    return function(value) {
-      return f(k * value) + prefix;
-    };
+        prefix = prefixes[(-1 * minimumPrefixOrder) + e / 3];
+      return function (value) {
+        return f(k * value) + prefix;
+      };
+    }
   }
 
+  var formatPrefix = createFormatPrefix(SIprefixes, -8, 8);
+  var formatCurrencyPrefix = createFormatPrefix(currencyAbbreviations, 0, currencyAbbreviations.length - 1);
+
   return {
     format: newFormat,
+    formatCurrencyPrefix: formatCurrencyPrefix,
     formatPrefix: formatPrefix
   };
 }

src/precisionPrefix.js

@@ -1,5 +1,9 @@
 import exponent from "./exponent.js";
 
-export default function(step, value) {
-  return Math.max(0, Math.max(-8, Math.min(8, Math.floor(exponent(value) / 3))) * 3 - exponent(Math.abs(step)));
+export function createPrecisionPrefix(minimumPrefixOrder, maximumPrefixOrder) {
+  return function (step, value) {
+    return Math.max(0, Math.max(minimumPrefixOrder, Math.min(maximumPrefixOrder, Math.floor(exponent(value) / 3))) * 3 - exponent(Math.abs(step)));
+  }
 }
+
+export default createPrecisionPrefix(-8, 8);

test/currencyPrecisionPrefix-test.js

@@ -0,0 +1,52 @@
+var tape = require("tape"),
+    format = require("../");
+
+// For currencies, only 4 prefixes are commonly used:
+// thousands (K), millions (M), billions (B) and trillions (T)
+
+tape("precisionPrefix(step, value) returns zero between 1 and 100 (unit step)", function (test) {
+  test.equal(format.currencyPrecisionPrefix(1e+0, 1e+0), 0); // 1
+  test.equal(format.currencyPrecisionPrefix(1e+0, 1e+1), 0); // 10
+  test.equal(format.currencyPrecisionPrefix(1e+0, 1e+2), 0); // 100
+  test.end()
+});
+
+tape("precisionPrefix(step, value) returns zero between 1 and 100 (thousand step)", function (test) {
+  test.equal(format.currencyPrecisionPrefix(1e+3, 1e+3), 0); // 1K
+  test.equal(format.currencyPrecisionPrefix(1e+3, 1e+4), 0); // 10K
+  test.equal(format.currencyPrecisionPrefix(1e+3, 1e+5), 0); // 100K
+  test.end()
+});
+
+tape("precisionPrefix(step, value) returns zero between 1 and 100 (million step)", function (test) {
+  test.equal(format.currencyPrecisionPrefix(1e+6, 1e+6), 0); // 1M
+  test.equal(format.currencyPrecisionPrefix(1e+6, 1e+7), 0); // 10M
+  test.equal(format.currencyPrecisionPrefix(1e+6, 1e+8), 0); // 100M
+  test.end()
+});
+
+tape("precisionPrefix(step, value) returns zero between 1 and 100 (billion step)", function (test) {
+  test.equal(format.currencyPrecisionPrefix(1e+9, 1e+9), 0); // 1B
+  test.equal(format.currencyPrecisionPrefix(1e+9, 1e+10), 0); // 10B
+  test.equal(format.currencyPrecisionPrefix(1e+9, 1e+11), 0); // 100B
+  test.end()
+});
+
+tape("currencyPrecisionPrefix(step, value) returns the expected precision when value is greater than one trillion", function(test) {
+  test.equal(format.currencyPrecisionPrefix(1e+12, 1e+12), 0); // 1T
+  test.equal(format.currencyPrecisionPrefix(1e+12, 1e+13), 0); // 10T
+  test.equal(format.currencyPrecisionPrefix(1e+12, 1e+14), 0); // 100T
+  test.equal(format.currencyPrecisionPrefix(1e+12, 1e+15), 0); // 1000T
+  test.equal(format.currencyPrecisionPrefix(1e+11, 1e+15), 1); // 1000.0T
+  test.end();
+});
+
+tape("currencyPrecisionPrefix(step, value) returns the expected precision when value is less than one unit", function(test) {
+  test.equal(format.currencyPrecisionPrefix(1e+0, 1e+0), 0); // 1
+  test.equal(format.currencyPrecisionPrefix(1e-1, 1e-1), 1); // 0.1
+  test.equal(format.currencyPrecisionPrefix(1e-2, 1e-2), 2); // 0.01
+  test.equal(format.currencyPrecisionPrefix(1e-3, 1e-3), 3); // 0.001
+  test.equal(format.currencyPrecisionPrefix(1e-4, 1e-4), 4); // 0.0001
+  test.end();
+});
+