StatControlCharts.QCWestgardRules Function

Compares values agains Westgard rules.

Pascal

procedure QCWestgardRules(const Data: TVec; const OutControl: TVec; dataMean: double; dataSigma: double);

File

StatControlCharts

Parameters

Parameters	Description
Data	Data to-be-checked with Westgard rules.
OutControl	Vector storing each point status. If point(i) is out-of-control, then OutControl.Values[i] will be greater than zero (see explanation above).
dataMean	In most cases equal to data mean, but you can specify any value.
dataSigma	In most cases equal to data standard deviation, but you can specify any value.

Description

Data individual values are tested to determine if they are in, or out, of control using a set of five rules called the Westgard rules. These rules indicate which points are out-of-control. The Westgard rules are (see www.westgard.com/mltirule.htmfor details):

Description	Rule
1S3	One value beyond three sigma from the mean.
1S2	One value beyond two sigma from the mean.
2S2	Two consecutive values either greater than, or less than, two sigma from the mean.
RS4	A difference between consecutive values greater than four sigma.
41S	Four consecutive values greater than, or less than, one sigma from the mean.
10X	Ten consecutive values all greater than, or less than, the mean.

For each point several rules can be violated at the same time. Each Westgard rule violation has different value:

Rule violated	Value
1S3	1=2^0
1S2	2=2^1
2S2 *	4=2^2
RS4	8=2^3
4S1	16=2^4
10X *	32=2^5

For example, if rules 2S2 and 10X were violated, then the sum of violations for point would be 4 + 32 = 36 = 100100.

Example

>Load process data, then check if any points are out-of-control.

Uses MtxExpr, StatControlCharts;
procedure Example;
var data, outofcontrol,indexes: Vector;
begin
  data.LoadFromFile('process_data.vec');
  QCWestgardRules(data,outofcontrol,data.mean,data.stddev);
  // Now find indexes of out-of-control points
  indexes.FindIndexes(outofcontrol,'>',0);
  // indexes.IValues now stores the indices of out-of-control points
end;

#include "MtxExpr.hpp"
#include "MtxExprInt.hpp"
#include "StatControlCharts.hpp"
void __fastcall Example()
{
      sVector data, outofcontrol;
    VectorInt indexes;

    data.LoadFromFile("process_data.vec");
    QCWestgardRules(data,outofcontrol,data.Mean(),data.StdDev());
    // Now find indexes of out-of-control points
      indexes.FindIndexes(outofcontrol,">",0.0);
}

StatControlCharts, Functions, Example

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