qualityTools (version 1.31.1)

pcr: Calculate the process capability ratios for a given dataset and distribution

Description

Calculates the process capability ratios cp, cpk, cpkL and cpkU for a given dataset and distribution. A histogramm with a density curve is displayed along with the specification limits and a Quantile-Quantile Plot for the specified distribution

Usage

pcr(x, distribution = "normal", lsl, usl, target, boxcox = FALSE, lambda, main, xlim, ylim, grouping = NULL, std.dev = NULL, conf.level = 0.9973002, start, lineWidth = 2, lineCol = "red", lineType = "solid", specCol = "black", specWidth = 2, cex.text = 2, cex.val = 1.5, cex.col = "darkgray", ...)

Arguments

x

numeric vector

distribution

character string such as "weibull"

lsl

lower specification limit

usl

upper specification limit

target

target value

boxcox

perform a Box-Cox transformation (default is FALSE)

lambda

lambda for the transformation

main

main

xlim

xlim

ylim

ylim

grouping

grouping vector

std.dev

historical standard devation (only for normal distribution)

conf.level

start

A named list giving the parameters to be fitted with initial values. Must be supplied for some distribution. (see Details)

lineWidth

the width of the line for the density curve

lineCol

the color of the line for the density curve

lineType

the line Type e.g. "dashed", "solid", etc.

specCol

col for the specification limits

specWidth

lwd for the specification limits

cex.text

cex for lsl, usl and target

cex.val

cex for the process capability ratios

cex.col

col for lsl, usl and target

...

other graphical parameters (par)

Details

Distribution fitting is deligated to function fitdistr of the R-package MASS.

See Also

qqPlot, ppPlot

Examples

#process capability for a weibull distribution
x = rweibull(30, 2, 8)
pcr(x, "weibull", lsl = 0, usl = 17)

#process capability assuming a normal distribution
pcr(x, "normal", lsl = 0, usl = 17)