Module spc 

Statistical Process Control (SPC) charts.

Provides control chart implementations for both variables and attributes data.

Variables Charts

• XBarRChart — X-bar and Range chart for subgroup data (n=2..=25)
• XBarSChart — X-bar and Standard Deviation chart for subgroup data (n=2..=25)
• IndividualMRChart — Individual and Moving Range chart for individual observations

Attributes Charts

• PChart — Proportion nonconforming (variable sample size)
• NPChart — Count of nonconforming items (constant sample size)
• CChart — Count of defects per unit (constant area of opportunity)
• UChart — Defects per unit (variable area of opportunity)

Run Rules

• RuleSet — any subset of the eight tests; RuleSet::nelson is the default
• WesternElectricRules — the 4 classic run rules
• NelsonRules — 8 rules (superset of Western Electric)

References

• Montgomery, D.C. (2019). Introduction to Statistical Quality Control, 8th ed.
• ASTM E2587 — Standard Practice for Use of Control Charts
• Nelson, L.S. (1984). “The Shewhart Control Chart — Tests for Special Causes”, Journal of Quality Technology 16(4), pp. 237-239.

Structs

AttributeChartPoint

A single data point on an attributes control chart.

CChart

Count of defects per unit (C) chart.

ChartPoint

A single point on a control chart.

ControlLimits

Control limits for a chart.

GChart

G chart (geometric distribution) result for rare-event monitoring.

GChartPoint

A single data point on a G or T chart.

IndividualMRChart

Individual and Moving Range (I-MR) control chart.

LaneyAttributePoint

A single data point for a Laney P’ or U’ chart.

LaneyPChart

Laney P’ chart result.

LaneyUChart

Laney U’ chart result.

NPChart

Count of nonconforming items (NP) chart.

NelsonRules

Nelson rules (8 rules, superset of Western Electric).

PChart

Proportion nonconforming (P) chart.

RuleSet

A chosen subset of the eight run tests.

TChart

T chart (exponential distribution) result for rare-event monitoring.

TChartPoint

A single data point on a T chart.

UChart

Defects per unit (U) chart.

Violation

A violation detected on the chart.

WesternElectricRules

Western Electric rules (4 rules).

XBarRChart

X-bar and Range (X-bar-R) control chart.

XBarSChart

X-bar and Standard Deviation (X-bar-S) control chart.

Enums

ControlChartError

Errors returned when a control chart cannot be constructed or cannot take a sample.

ViolationType

Types of control chart violations based on Nelson’s eight rules.

Constants

MAX_SUBGROUP_SIZE

Largest subgroup size the variables-chart factor tables cover.

MIN_SUBGROUP_SIZE

Smallest subgroup size the variables-chart factor tables cover.

Traits

ControlChart

Trait for control charts that process subgroup or individual data.

RunRule

Trait for applying run rules to chart data.

Functions

g_chart

Compute the G chart from inter-event conforming counts.

laney_p_chart

Compute the Laney P’ chart from (defective_count, sample_size) pairs.

laney_u_chart

Compute the Laney U’ chart from (defect_count, inspection_units) pairs.

t_chart

Compute the T chart from inter-event times.