StatisticalTestShewhart¶

class StatisticalTestShewhart¶

Bases: StatisticalTestSigma

Class that permits a Shewhart’s test.

Be \(s(t)\) the signal to monitor, \(\mu\) and \(\sigma\) the mean and standard deviation of this signal when it is “in control”.

A downward alarm is raised if: \(s(t) >= \mu - 3 \sigma\)

An upward alarm is raised if: \(s(t) >= \mu + 3 \sigma\)

Additionnally, we can activate the WECO’s rules that have been proposed by the Western Electric Company to add additionnal verifications:

An alarm is raised if two out of three consecutive points fall beyond the \(2\sigma\) -limit, on the same side of the mean \(\mu\)
An alarm is raised if four out of five consecutive points fall beyond the \(1\sigma\) -limit, on the same side of the mean \(\mu\)
An alarm is raised if eight consecutive points fall on the same side of the mean \(\mu\) .

The user can decide to use or not the WECO’s rules. Additionnally, the user can choose which WECO’s rule(s) to activate.

To detect only downward drifts of the input signal \(s(t)\) use testDownwardMeanDrift() .To detect only upward drifts in \(s(t)\) use testUpwardMeanDrift() . To detect both, downward and upward drifts use testDownUpwardMeanDrift() .

Methods

`__init__`
`getAlarm`	Get the alarm raised by the last test due to the WECO's rules.
`getSignal`	Overloaded function.
`getSignals`	Get the NB_DATA_SIGNAL last signal values, sorted from the latest [0] to the newest [NB_DATA_SIGNAL - 1].
`vpWecoRulesAlarmToString`

Inherited Methods

`getAvailableMeanDriftType`	Get the list of available vpMeanDriftType objects that are handled.
`setMinStdev`	Set the minimum value of the standard deviation that is expected.
`testUpwardMeanDrift`	Test if an upward mean drift occurred according to the new value of the signal.
`MEAN_DRIFT_DOWNWARD`
`MEAN_DRIFT_NONE`
`setNbSamplesForStat`	Set the number of samples required to compute the mean and standard deviation of the signal and allocate the memory accordingly.
`getStdev`	Get the standard deviation used as reference.
`testDownUpwardMeanDrift`	Test if a downward or an upward mean drift occurred according to the new value of the signal.
`MeanDriftType`	Enum that indicates if a drift of the mean occurred.
`init`	Overloaded function.
`vpMeanDriftTypeToString`
`MEAN_DRIFT_BOTH`
`MEAN_DRIFT_UNKNOWN`
`vpMeanDriftTypeFromString`	Cast a string into a vpMeanDriftType .
`getLimits`	Get the upper and lower limits of the test signal.
`MEAN_DRIFT_UPWARD`
`MEAN_DRIFT_COUNT`
`testDownwardMeanDrift`	Test if a downward mean drift occurred according to the new value of the signal.
`print`
`getMean`	Get the mean used as reference.

Operators

`__doc__`
`__init__`
`__module__`

Attributes

`COUNT_WECO`
`MEAN_DRIFT_BOTH`
`MEAN_DRIFT_COUNT`
`MEAN_DRIFT_DOWNWARD`
`MEAN_DRIFT_NONE`
`MEAN_DRIFT_UNKNOWN`
`MEAN_DRIFT_UPWARD`
`NB_DATA_SIGNAL`
`NONE_WECO`
`ONE_SIGMA_WECO`
`SAME_SIDE_WECO`
`THREE_SIGMA_WECO`
`TWO_SIGMA_WECO`
`__annotations__`

class MeanDriftType(self, value: int)¶

Bases: pybind11_object

Enum that indicates if a drift of the mean occurred.

Values:

MEAN_DRIFT_NONE: No mean drift occurred
MEAN_DRIFT_DOWNWARD: A downward drift of the mean occurred.
MEAN_DRIFT_UPWARD: An upward drift of the mean occurred.
MEAN_DRIFT_BOTH: Both an aupward and a downward drifts occurred.
MEAN_DRIFT_COUNT
MEAN_DRIFT_UNKNOWN

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

class WecoRulesAlarm(self, value: int)¶

Bases: pybind11_object

Values:

THREE_SIGMA_WECO: When a \(3\sigma\) alarm was raised.
TWO_SIGMA_WECO: When a \(2\sigma\) alarm was raised.
ONE_SIGMA_WECO: When a \(1\sigma\) alarm was raised
SAME_SIDE_WECO: When a alarm raised when 8 consecutive points lie on the same side of the mean \(\mu\) was raised.
NONE_WECO: When no WECO’s rule alarm was raised.
COUNT_WECO: Number of WECO’s rules that are implemented.

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

__init__(*args, **kwargs)¶

getAlarm(self) → visp._visp.core.StatisticalTestShewhart.WecoRulesAlarm¶

Get the alarm raised by the last test due to the WECO’s rules.

Returns:: vpWecoRulesAlarm The type of raised alarm.

static getAvailableMeanDriftType(prefix: str = <, sep: str =, suffix: str = >) → str¶

Get the list of available vpMeanDriftType objects that are handled.

Parameters:

prefix: The prefix that should be placed before the list.
sep: The separator between each element of the list.
suffix: The suffix that should terminate the list.

Returns:

std::string The list of handled type of process tests, presented as a string.

getLimits(self, limitDown: float, limitUp: float) → tuple[float, float]¶

Get the upper and lower limits of the test signal.

Parameters:

limitDown: float¶: The lower limit.
limitUp: float¶: The upper limit.

Returns:

A tuple containing:

limitDown: The lower limit.
limitUp: The upper limit.

getMean(self) → float¶

Get the mean used as reference.

Returns:: float The mean.

getSignal(*args, **kwargs)¶

Overloaded function.

getSignal(self: visp._visp.core.StatisticalTestShewhart) -> float

Get the last value of the signal.

Returns:: float The signal.

getSignal(self: visp._visp.core.StatisticalTestSigma) -> float

Get the last value of the signal.

Returns:: float The signal.

getSignals(self) → list[float]¶

Get the NB_DATA_SIGNAL last signal values, sorted from the latest [0] to the newest [NB_DATA_SIGNAL - 1].

Returns:: std::vector<float> The last NB_DATA_SIGNAL values.

getStdev(self) → float¶

Get the standard deviation used as reference.

Returns:: float The standard deviation.

init(*args, **kwargs)¶

Overloaded function.

init(self: visp._visp.core.StatisticalTestSigma, h: float = 3.f, nbSamplesForStats: int = 30) -> None

(Re)Initialize the test.

Parameters:

h: The alarm factor applied to the standard deviation to compute the limits.
nbSamplesForStats: The number of samples to compute the statistics of the signal.

init(self: visp._visp.core.StatisticalTestSigma, h: float, mean: float, stdev: float) -> None

(Re)Initialize the test.

Parameters:

h: The alarm factor applied to the standard deviation to compute the limits.
mean: The expected mean of the signal.
stdev: The expected standard deviation of the signal.

init(self: visp._visp.core.StatisticalTestAbstract) -> None

(Re)Initialize the algorithm.

static print(type: visp._visp.core.StatisticalTestAbstract.MeanDriftType) → None¶

setMinStdev(self, stdevmin: float) → None¶

Set the minimum value of the standard deviation that is expected. The computed standard deviation cannot be lower this value if set.

Parameters:

stdevmin: float¶: The minimum value of the standard deviation that is expected.

setNbSamplesForStat(self, nbSamples: int) → None¶

Set the number of samples required to compute the mean and standard deviation of the signal and allocate the memory accordingly.

Parameters:

nbSamples: int¶: The number of samples we want to use.

testDownUpwardMeanDrift(self, signal: float) → visp._visp.core.StatisticalTestAbstract.MeanDriftType¶

Test if a downward or an upward mean drift occurred according to the new value of the signal.

Note

See testDownwardMeanDrift() testUpwardMeanDrift()

Parameters:

signal: float¶: The new value of the signal.

Returns:

vpMeanDriftType The type of mean drift that occurred.

testDownwardMeanDrift(self, signal: float) → visp._visp.core.StatisticalTestAbstract.MeanDriftType¶

Test if a downward mean drift occurred according to the new value of the signal.

Note

See testUpwardMeanDrift()

Parameters:

signal: float¶: The new value of the signal.

Returns:

vpMeanDriftType The type of mean drift that occurred.

testUpwardMeanDrift(self, signal: float) → visp._visp.core.StatisticalTestAbstract.MeanDriftType¶

Test if an upward mean drift occurred according to the new value of the signal.

Note

See testDownwardMeanDrift()

Parameters:

signal: float¶: The new value of the signal.

Returns:

vpMeanDriftType The type of mean drift that occurred.

static vpMeanDriftTypeFromString(name: str) → visp._visp.core.StatisticalTestAbstract.MeanDriftType¶

Cast a string into a vpMeanDriftType .

Parameters:

name: str¶: The name of the mean drift.

Returns:

vpMeanDriftType The corresponding vpMeanDriftType .

static vpMeanDriftTypeToString(type: visp._visp.core.StatisticalTestAbstract.MeanDriftType) → str¶

static vpWecoRulesAlarmToString(alarm: visp._visp.core.StatisticalTestShewhart.WecoRulesAlarm) → str¶