fix grubbs test: use sampleStandardDeviation

Author: aozisik

package.json

@@ -1,6 +1,6 @@
 {
   "name": "labkar-algorithms",
-  "version": "5.3.1",
+  "version": "5.3.3",
   "description": "Labkar Algorithms",
   "main": "dist/lib.js",
   "author": "ODTÜ PAL",

src/algorithms/q-hampel.ts

@@ -1,6 +1,6 @@
 const { jStat } = require('jstat');
 import { median } from 'simple-statistics';
-import { get, sortBy, sumBy, round, sortedUniq, findIndex } from 'lodash';
+import { get, sortBy, sumBy, round, sortedUniq, findIndex, uniq } from 'lodash';
 
 import { Result } from '../types';
 
@@ -22,6 +22,15 @@ export function Q(
 ): Result {
   const { precision } = options;
 
+  if (!results.length) {
+    throw new Error('At least one test result is required to calculate Q');
+  }
+
+  // If all values are the same, return the first value
+  if (uniq(results).length === 1) {
+    return { value: results[0] };
+  }
+
   const values: number[] = ([] as number[]).concat(results).sort();
 
   let deltas = [];
@@ -36,6 +45,8 @@ export function Q(
   const sortedUniqueDeltas = sortedUniq(sortedDeltas);
   const hMultiplier = 2 / (results.length * (results.length - 1));
 
+  console.log(JSON.stringify({ sortedDeltas, sortedUniqueDeltas }, null, 2));
+
   const calculations: Q_Calculation[] = [];
 
   for (let i = 0; i < sortedUniqueDeltas.length; i++) {
@@ -53,6 +64,8 @@ export function Q(
     });
   }
 
+  console.log(calculations);
+
   // START OF Q Calc.
   const firstParameter = calculations[0].h1 * 0.75 + 0.25;
   const secondParameter = calculations[0].h1 * 0.375 + 0.625;

src/grubbs/index.ts

@@ -1,4 +1,4 @@
-import { average, standardDeviation } from 'simple-statistics';
+import { average, sampleStandardDeviation } from 'simple-statistics';
 import criticalValueTable from './criticalValueTable';
 
 export type GrubbsResult = {
@@ -17,7 +17,7 @@ export function grubbs(
   originOptions: { alpha: number }
 ): GrubbsResult[] {
   if (typeof originDataSet === 'undefined') {
-    throw new Error('dataSet MUST be passed');
+    throw new Error('dataSet MUST be passed');
   } else if (originDataSet.filter(isValidData).length > 500) {
     throw new Error('dataSet.length MUST less than 500');
   } else if (originDataSet.filter(isValidData).length <= 2) {
@@ -58,7 +58,7 @@ export function grubbs(
     done = true;
     currentRound = {};
     currentRound.dataSet = dataSet.slice();
-    currentRound.stdev = standardDeviation(
+    currentRound.stdev = sampleStandardDeviation(
       currentRound.dataSet.filter(isValidData)
     );
     currentRound.average =

tests/algorithms.test.ts

@@ -63,6 +63,26 @@ describe('Algorithms', () => {
     // expect(output.hampel).toBeCloseTo(44.722, 3);
   });
 
+  it('Q/Hampel Method (samples with no variance)', () => {
+    const samples = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+
+    const q = Q(samples);
+    const hampel = Hampel(samples, q.value);
+
+    expect(q.value).toBe(1);
+    expect(hampel.value).toBe(1);
+  });
+
+  it.only('Q/Hampel Method (samples with low variance)', () => {
+    const samples = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1.1, 1, 1, 1, 1, 1, 1];
+
+    const q = Q(samples);
+    const hampel = Hampel(samples, q.value);
+
+    expect(q.value).toBeCloseTo(1.0040785270846, 4);
+    expect(hampel.value).toBeCloseTo(0.040785270845889, 4);
+  });
+
   it('Hampel Method', () => {
     const samples = [
       41.41, 39.22, 47.29, 82.46, 45.24, 49.96, 38.2, 45.41, 39.82, 48.17,

tests/grubbs.test.ts

@@ -8,7 +8,22 @@ describe('Grubbs test', () => {
     });
 
     expect(result[0].outlierIndexes).toEqual([4]);
-    expect(result[0].stdev).toEqual(29.7);
+    expect(result[0].stdev).toBeCloseTo(31.31, 2);
+  });
+
+  it('Only -60 is outlier in this group', () => {
+    const results = grubbs([-60, -55.6, -54.7, -54.6, -54.5, -54.4, -54.1], {
+      alpha: 0.01,
+    });
+
+    // console.log(results);
+
+    // Find all outlier indexes
+    const outlierIndexes = results
+      .map((result) => result.outlierIndexes)
+      .flat();
+
+    expect(outlierIndexes).toEqual([0]);
   });
 
   it.skip('calculates for %1', () => {