Process capability indices (parametric)

Description

Calculates Cpk, Cpmk using the formulation described by Kerstin Vannman(1995).

Usage

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qcs.cp(object, parameters = c(u = 0, v = 0), limits = c(lsl = -3, usl = 3),
  target = NULL, mu = 0, std.dev = 1, nsigmas = 3, k = 1,
  contour = TRUE, ylim = NULL, ...)

Arguments

object

qcs object of type "qcs.xbar" or "qcs.one".

parameters

A vector specifying the u and v parameters values. If parameters = c(u=0, v=0), the cp indice is calculed; If parameters = c(u=1, v=0), the cpk indice is calculed; If parameters = c(u=0, v=1), the cpm indice is calculed; If parameters = c(u=1, v=1), the cpmk indice is calculed.

limits

A vector specifying the lower and upper specification limits.

target

A value specifying the target of the process. If is NULL, the target is set at the middle value bewteen specification limits.

mu

A value specifying the mean of data.

std.dev

A value specifying the within-group standard deviation.

nsigmas

A numeric value specifying the number of sigmas to use.

k

A numeric value. If the capacity index exceeds the k value, then the process is capable.

contour

Logical value indicating whether contour graph should be plotted.

ylim

The y limits of the plot.

...

Arguments to be passed to or from methods.

References

Montgomery, D.C. (1991) Introduction to Statistical Quality Control, 2nd ed, New York, John Wiley & Sons.
Vannman, K (1995) A Unified Approach to Capability Indices. Statitica Sinica,5,805-820.

Examples

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library(qcr)
data(pistonrings) 
xbar <- qcs.xbar(pistonrings[1:125,],plot = TRUE)
mu <-xbar$center
std.dev <-xbar$std.dev
LSL=73.99; USL=74.01
qcs.cp(parameters = c(0,0),limits = c(LSL,USL),
      mu = mu,std.dev = std.dev,ylim=c(0,1))
#calculating all the indices
qcs.cp(object = xbar,parameters = c(0,0), limits = c(LSL,USL),ylim=c(0,1))
qcs.cp(object = xbar,parameters = c(1,0), limits = c(LSL,USL),ylim=c(0,1))
qcs.cp(object = xbar,parameters = c(0,1), limits = c(LSL,USL),ylim=c(0,1))
qcs.cp(object = xbar,parameters = c(1,1), limits = c(LSL,USL),ylim=c(0,1))

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