ml-random - npm Package Compare versions

Comparing version 0.2.0 to 0.3.0

History.md

@@ -0,1 +1,6 @@
+<a name="0.3.0"></a>
+# [0.3.0](https://github.com/mljs/random/compare/v0.2.0...v0.3.0) (2018-05-23)
+
+
+
 <a name="0.2.0"></a>
@@ -2,0 +7,0 @@ # [0.2.0](https://github.com/mljs/random/compare/v0.1.0...v0.2.0) (2018-05-16)

lib-es6/choice.js

 function randomChoice(values, options = {}, random = Math.random) {
-    const { size = 1, replace = false } = options;
+    const { size = 1, replace = false, probabilities } = options;
     let valuesArr;
+    let cumSum;
     if (typeof values === 'number') {
@@ -10,2 +11,18 @@ valuesArr = getArray(values);
     }
+    if (probabilities) {
+        if (!replace) {
+            throw new Error('choice with probabilities and no replacement is not implemented');
+        }
+        // check input is sane
+        if (probabilities.length !== valuesArr.length) {
+            throw new Error('the length of probabilities option should be equal to the number of choices');
+        }
+        cumSum = [probabilities[0]];
+        for (let i = 1; i < probabilities.length; i++) {
+            cumSum[i] = cumSum[i - 1] + probabilities[i];
+        }
+        if (Math.abs(1 - cumSum[cumSum.length - 1]) > Number.EPSILON) {
+            throw new Error('probabilities should sum to 1');
+        }
+    }
     if (replace === false && size > valuesArr.length) {
@@ -16,3 +33,3 @@ throw new Error('size option is too large');
     for (let i = 0; i < size; i++) {
-        const index = randomIndex(valuesArr.length, random);
+        const index = randomIndex(valuesArr.length, random, cumSum);
         result.push(valuesArr[index]);
@@ -32,5 +49,15 @@ if (!replace) {
 }
-function randomIndex(n, random) {
-    return Math.floor(random() * n);
+function randomIndex(n, random, cumSum) {
+    const rand = random();
+    if (!cumSum) {
+        return Math.floor(rand * n);
+    }
+    else {
+        let idx = 0;
+        while (rand > cumSum[idx]) {
+            idx++;
+        }
+        return idx;
+    }
 }
 export default randomChoice;

lib/choice.js

 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
 function randomChoice(values, options = {}, random = Math.random) {
-    const { size = 1, replace = false } = options;
+    const { size = 1, replace = false, probabilities } = options;
     let valuesArr;
+    let cumSum;
     if (typeof values === 'number') {
@@ -12,2 +13,18 @@ valuesArr = getArray(values);
     }
+    if (probabilities) {
+        if (!replace) {
+            throw new Error('choice with probabilities and no replacement is not implemented');
+        }
+        // check input is sane
+        if (probabilities.length !== valuesArr.length) {
+            throw new Error('the length of probabilities option should be equal to the number of choices');
+        }
+        cumSum = [probabilities[0]];
+        for (let i = 1; i < probabilities.length; i++) {
+            cumSum[i] = cumSum[i - 1] + probabilities[i];
+        }
+        if (Math.abs(1 - cumSum[cumSum.length - 1]) > Number.EPSILON) {
+            throw new Error('probabilities should sum to 1');
+        }
+    }
     if (replace === false && size > valuesArr.length) {
@@ -18,3 +35,3 @@ throw new Error('size option is too large');
     for (let i = 0; i < size; i++) {
-        const index = randomIndex(valuesArr.length, random);
+        const index = randomIndex(valuesArr.length, random, cumSum);
         result.push(valuesArr[index]);
@@ -34,5 +51,15 @@ if (!replace) {
 }
-function randomIndex(n, random) {
-    return Math.floor(random() * n);
+function randomIndex(n, random, cumSum) {
+    const rand = random();
+    if (!cumSum) {
+        return Math.floor(rand * n);
+    }
+    else {
+        let idx = 0;
+        while (rand > cumSum[idx]) {
+            idx++;
+        }
+        return idx;
+    }
 }
 exports.default = randomChoice;

lib/Options.d.ts

@@ -13,2 +13,6 @@ /**
     replace?: boolean;
+    /**
+     * The probabilities associated with each element. Probabilities should sum to 1 and be the same length as the values. If not specified a uniform distribution is assumed.
+     */
+    probabilities?: number[];
 }

package.json

 {
   "name": "ml-random",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "choose randomly from a selection of elements",
@@ -15,2 +15,3 @@ "main": "lib/index.js",
     "test-only": "jest",
+    "test-coverage": "jest --coverage",
     "tsc": "run-s clean tsc-es6 tsc-es5",
@@ -17,0 +18,0 @@ "tsc-es5": "tsc",

src/__tests__/test.ts

@@ -53,2 +53,36 @@ import * as XSAdd from 'ml-xsadd';
   });
+
+  it('should produce choice given probabilities', () => {
+    const samples = 10000;
+    const r = random.choice(2, {
+      size: samples,
+      replace: true,
+      probabilities: [0.3, 0.7]
+    });
+    const count = r.reduce(
+      (prev, current) => (current === 0 ? prev + 1 : prev),
+      0
+    );
+    expect(count / samples).toBeCloseTo(0.3, 2);
+  });
+
+  it('should throw if probabilities option has the wrong size', () => {
+    expect(() => {
+      random.choice(3, { replace: true, probabilities: [0.5, 0.5] });
+    }).toThrow(
+      'the length of probabilities option should be equal to the number of choices'
+    );
+  });
+
+  it('should throw if probabilities option does not sum to 1', () => {
+    expect(() => {
+      random.choice(3, { replace: true, probabilities: [0.1, 0.5, 0.4001] });
+    }).toThrow('probabilities should sum to 1');
+  });
+
+  it('choice with probabilities and no replacement not implemented', () => {
+    expect(() => {
+      random.choice(3, { replace: false, probabilities: [0.1, 0.5, 0.4] });
+    }).toThrow(/not implemented/);
+  });
 });
@@ -55,0 +89,0 @@

src/choice.ts

@@ -19,4 +19,6 @@ import { IChoiceOptions } from './Options';
 ): Array<T | number> {
-  const { size = 1, replace = false } = options;
+  const { size = 1, replace = false, probabilities } = options;
+
   let valuesArr;
+  let cumSum;
   if (typeof values === 'number') {
@@ -28,2 +30,24 @@ valuesArr = getArray(values);
 
+  if (probabilities) {
+    if (!replace) {
+      throw new Error(
+        'choice with probabilities and no replacement is not implemented'
+      );
+    }
+    // check input is sane
+    if (probabilities.length !== valuesArr.length) {
+      throw new Error(
+        'the length of probabilities option should be equal to the number of choices'
+      );
+    }
+    cumSum = [probabilities[0]];
+    for (let i = 1; i < probabilities.length; i++) {
+      cumSum[i] = cumSum[i - 1] + probabilities[i];
+    }
+
+    if (Math.abs(1 - cumSum[cumSum.length - 1]) > Number.EPSILON) {
+      throw new Error('probabilities should sum to 1');
+    }
+  }
+
   if (replace === false && size > valuesArr.length) {
@@ -34,3 +58,3 @@ throw new Error('size option is too large');
   for (let i = 0; i < size; i++) {
-    const index = randomIndex(valuesArr.length, random);
+    const index = randomIndex(valuesArr.length, random, cumSum);
     result.push(valuesArr[index]);
@@ -52,6 +76,15 @@ if (!replace) {
 
-function randomIndex(n: number, random: IRandomGenerator) {
-  return Math.floor(random() * n);
+function randomIndex(n: number, random: IRandomGenerator, cumSum?: number[]) {
+  const rand = random();
+  if (!cumSum) {
+    return Math.floor(rand * n);
+  } else {
+    let idx = 0;
+    while (rand > cumSum[idx]) {
+      idx++;
+    }
+    return idx;
+  }
 }
 
 export default randomChoice;

src/Options.ts

@@ -13,2 +13,6 @@ /**
   replace?: boolean;
+  /**
+   * The probabilities associated with each element. Probabilities should sum to 1 and be the same length as the values. If not specified a uniform distribution is assumed.
+   */
+  probabilities?: number[];
 }

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Improved metrics

Total package byte prevSize

19302

increased by28.47%

Lines of code

463

increased by35.78%

No dependency changes