Classical plots of Mandel's statistics.
Description
plot.mandel.kh
produces classic plots of Mandel's statistics, suitably
grouped and with appropriate indicator lines for unusual values.
Usage
1 2 3 4 5 6 7 8 9 10  ## S3 method for class 'mandel.kh'
plot(x, probs = c(0.95, 0.99), main, xlab = attr(x, "grouped.by"),
ylab = attr(x, "mandel.type"), ylim = NULL, las = 1,
axes = TRUE, cex.axis = 1, frame.plot = axes,
lwd = 1, lty = 1, col = par("col"),
col.ind = 1, lty.ind = c(2, 1), lwd.ind = 1,
separators = TRUE, col.sep = "lightgrey", lwd.sep = 1, lty.sep = 1,
zero.line = TRUE, lwd.zero = 1, col.zero = 1, lty.zero = 1,
p.adjust = "none", ...)

Arguments
x 
An object of class 
probs 
Indicator lines are drawn for these probabilities. Note that

main 
a main title for the plot. If missing, the default is

xlab 
a label for the x axis; defaults to the 
ylab 
a label for the x axis; defaults to the 
ylim 
the y limits of the plot. For Mandel's k, the default lower limit is zero. 
las 
the style of the axis labels; see 
axes 
a logical value indicating whether axes should be drawn on the plot. 
cex.axis 
The magnification to be used for axis annotation relative to the current setting of 'cex'. 
frame.plot 
Logical; If 
lwd, lty, col 
Graphical parameters used for the plotted vertical lines corresponding to each value of Mandel's statistics (the plot is of type "h"). All are recycled across the prinmary grouping factor, allowing different measurands/test items to be identified more clearly. 
col.ind, lty.ind, lwd.ind 
Graphical parameters used for the indicator lines, recyckled to 
separators 
Logical; if 
col.sep, lwd.sep, lty.sep 
Graphical parameters used for the separator lines. 
zero.line 
logical; if 
lwd.zero, col.zero, lty.zero 
Graphical parameters used for the zero line. 
p.adjust 
Correction method for probabilities. If not 
... 
Other (usually graphical) parameters passed to 
Details
Mandel's statistics are traditionally plotted for interlaboratory study data,
grouped by laboratory, to give a rapid graphical view of laboratory bias and
relative precision. The traditional plot is a plot of type "h"
, that is,
simple vertical lines from the xaxis.
For classical Mandel statistics, indicator lines are drawn based on qmandelh
or qmandelk
as appropriate. For robust variants, indicator lines use
qnorm
for the h statistic and qf(probs, n, Inf)
for
the k statistic. Note that this corresponds to taking the robust estimates of
location and scale as true values, so will be somewhat anticonservative.
plot.mandel.kh
uses gplot
for the main plot.
Value
plot.mandel.kh returns a numeric vector of midpoints of the groups along the xaxis.
Author(s)
S Ellison s.ellison@lgc.co.uk
References
Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method. ISO, Geneva (1994).
See Also
mandel.h
, mandel.k
, mandel.kh
,
pmandelh
, pmandelk
for probabilities, quantiles etc.
See barplot.mandel.kh
for an alternative plotting method.
gplot
for the underlying plotting function.
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13 14  data(RMstudy)
h < with(RMstudy, mandel.h(RMstudy[2:9], g=Lab))
plot(h, las=2) # Lab 4 shows consistent low bias;
# Lab 23 several extreme values.
#Use colours to identify particular measurands:
plot(h, las=2, col=1:8)
legend("bottomleft", legend=names(h), col=1:8, lty=1, cex=0.7, bg="white")
#Example of Mandel's k:
k < with(RMstudy, mandel.k(RMstudy[2:9], g=Lab))
plot(k, las=2) # Lab 8 looks unusually variable;
# Lab 14 unusually precise
