Shewhart Controls
A simple library that applies Shewhart chart rules to an array of numbers.
Install
npm install --save @lucasheight/shewhartcontrols
Using
Create a new ShewhartControls object with an array of numbers.
const data: IShewhartResult = new ShewhartControls([9, 2, 5, 4, 12, 7]);Optionally:
- Provide a boolean (useSampleStDev) to indicate standard deviation method to use. (defaults to true: Sample Standard Deviation). Set to false if you wish to apply population standard deviation.
Results
ShewhartControls: {
data: [ 9, 2, 5, 4, 12, 7 ],
useSampleStDev: true,
points: [
{ value: 9, violations: [Object] },
{ value: 2, violations: [Object] },
{ value: 5, violations: [Object] },
{ value: 4, violations: [Object] },
{ value: 12, violations: [Object] },
{ value: 7, violations: [Object] }
],
mean: 6.5,
stDev: 3.6193922141707713,
posSigma1: 10.119392214170771,
posSigma2: 13.738784428341543,
posSigma3: 17.358176642512312,
negSigma1: 2.8806077858292287,
negSigma2: -0.7387844283415426,
negSigma3: -4.358176642512314,
violations: {
ThreeSigmaViolation: false,
EightPointsAboveBelowMean: false,
InnerThird15ConsecutiveViolation: false,
SixPointTrend: false,
TwoOfThreeOuterThirdViolation: false
}
}Violations Object
The violations object contains booleans when rules have been violated. These violations are indicated for the whole dataset and individually for each data point.
export interface IViolations {
/** 1 Point Outside the +/−3 Sigma Limits */
ThreeSigmaViolation: boolean;
/** 8 Successive Consecutive Points Above (or Below) the Centerline */
EightPointsAboveBelowMean: boolean;
/** Six or More Consecutive Points Steadily Increasing or Decreasing */
SixPointTrend: boolean;
/** Two out of Three Successive Points in Zone A or Beyond */
TwoOfThreeOuterThirdViolation: boolean;
/** 15 Consecutive Points in Zone C on Either Side of the Centerline */
InnerThird15ConsecutiveViolation: boolean;
}