Lambda Plot

DESCRIPTION:

Displays a lambda plot using the results of a Box-Cox transformation analysis.

USAGE:

lambda(x, ...) 

REQUIRED ARGUMENTS:

x
x is an object of class "boxcox", typically the output from performing a Box-Cox transformation analysis with boxcox.

OPTIONAL ARGUMENTS:

...
Graphical parameters may be supplied.

VALUE:

None.

SIDE EFFECTS:

A lambda plot is displayed on the current graphics device.

METHODS:

The t-values for all terms in the reduced model associated with a Box-Cox transformation are plotted against lambda values. A two-sided 95% confidence interval for significant effects is shown as well as the choice for the best lambda value.

REFERENCES:

Box, G.E.P (1988) Signal-to-noise ratios, performance criteria, and transformations. Technometrics, 30:1-17.

Box, G.E.P. and D.R. Cox (1964) An analysis of transformations (with discussion). J. Royal Statist. Soc. Ser. B, 26:211-246

Box, G.E.P. and C.A. Fung (1983) Some considerations in estimating data transformations. MRC Report #2609, University of Wisconsin-Madison.

Box, G.E.P. and C.A. Fung (1986) Studies in quality improvement: Minimizing transmitted variation by parameter design. Report 8, University of Wisconsin-Madison, Center for Quality and Productivity Improvement (submitted to the Journal of Quality Technology).

Box, G. E. P., W. G. Hunter, and J. S. Hunter (1978) Statistics for Experimenters, New York: Wiley.

Haaland, P. D. (1989) Experimental Design in Biotechnology, New York: Marcel Dekker.

SEE ALSO:

, , , .

EXAMPLES:

buffer.fac <- fac.aov(buffer.df) 
buffer.bc <- boxcox(buffer.fac, ~pH*thimer + pH*gent) 
lambda(bmi.bc)