controlrules
Western Electric and Nelson control rules
Description
returns violation indicators for the points in the numeric vector R
= controlrules(rules
,X
,cl
,se
)X
,
using the rules in rules
, center line values cl
and
standard errors se
. If X
contains
n points and rules
contains
m rules, then R
is an
n-by-m logical matrix, where
R(i,j)
has the value true
(logical
1
) if point i
violates rule j
,
and a value false
(logical 0
) if it does not. If
rules
contains only one control rule, then R
is
a logical vector of length n.
[
additionally returns a cell array containing the names of the applied control rules.R
,appliedRules
] = controlrules(___)
Examples
Use Western Electric Control Rule
Load the parts
data set.
load parts;
Create an X-bar chart with controlchart
using the we4
rule to mark out of control measurements. Return the subgroup statistics and plot data.
[stats,plotted] = controlchart(runout,rules="we4");
The software marks the out of control points marked with a red circle. Display the subgroup numbers of the out of control points.
find(plotted.ooc)
ans = 4×1
2
21
25
27
Use controlrules
to identify the measurements that violate the we4
control rule.
R = controlrules("we4",plotted.pts,plotted.cl(1),plotted.se(1));
I = find(R)
I = 27
The subgroups 2, 21, and 25 are out of control since they are outside the control limits delineated by the red lines. Subgroup 27 is in violation of the we4
control rule, since it is the last of eight consecutive points that lie above the center line.
Input Arguments
rules
— Control rules
character vector | string scalar | string array | cell array of character vectors
Control rules, specified as a character vector, string scalar, string array, or cell array of character vectors containing one or more of the following values.
Value | Violation Condition |
---|---|
"we1" | |
"we2" | Two of three points above |
"we3" | Four of five points above |
"we4" | Eight of eight points above cl |
"we5" | One point below |
"we6" | Two of three points below |
"we7" | Four of five points below |
"we8" | Eight of eight points below cl |
"we9" | 15 of 15 points between |
"we10" | Eight of eight points below |
"n1" | One point below |
"n2" | Nine of nine points on the same side of cl |
"n3" | Six of six points increasing or decreasing |
"n4" | 14 points alternating up or down |
"n5" | Two of three points below |
"n6" | Four of five points below |
"n7" | 15 of 15 points between |
"n8" | Eight of eight points below |
"we" | All Western Electric rules (beginning with the letters
"we" ) |
"n" | All Nelson rules (beginning with the letter
"n" ) |
For the control rules that involve more than a single point, a rule
violation at point i
indicates that the set of consecutive points
ending at point i
trigger the rule. R(i)
is
true
only if the point i
is one of the points
that violates the rule's condition.
Any point whose X
, cl
, or
se
value is NaN
is not counted in rules that
involve more than a single point, and always has an R
value of
false
(logical 0).
Example: rules=["we","n"]
Data Types: char
| string
X
— Points to evaluate
numeric vector
Points to evaluate, specified as a numeric vector.
Data Types: single
| double
cl
— Center lines
numeric vector | numeric scalar
Center lines, specified as a numeric vector that has the same length as
X
. You can also specify cl
as a numeric
scalar. In this case, the software uses the same value for all points.
Example: cl=1.5
Data Types: single
| double
se
— Standard errors
numeric vector | numeric scalar
Standard errors, specified as a numeric vector that has the same length as
X
. You can also specify se
as a numeric
scalar. In this case, the software uses the same value for all points.
Example: se=2.5
Data Types: single
| double
Output Arguments
R
— Control rule violation indicators
logical matrix | logical vector
Control rule violation indicators for the points in X
, using
the rules in rules
, center line values cl
, and
standard errors se
. If X
contains
n points and rules
contains
m rules, then R
is an
n-by-m logical matrix, where
R(i,j)
has the value true
(logical
1
) if point i
violates rule
j
, and a value false
(logical
0
) if it does not. If rules
contains only one
control rule, R
is a logical vector of length
n.
appliedRules
— Applied control rules
cell array of character vectors
Applied control rules, returned as a cell array of character vectors. If
rules
includes "we"
or "n"
,
all of the associated individual rules are included in
appliedRules
.
Version History
Introduced in R2006b
See Also
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