gamlss (version 4.2-4)

centiles.com: Comparing centiles from different GAMLSS models

Description

This function compares centiles curves for more than one GAMLSS objects.It is based on the centiles function. The function also tabulates the sample percentages below each centile curve (for comparison with the model percentages given by the argument cent.) A restriction of the function is that it applies to models with one explanatory variable only

Usage

centiles.com(obj, ..., xvar = NULL, cent = c(0.4, 10, 50, 90, 99.6), 
             legend = TRUE, ylab = "y", xlab = "x", xleg = min(xvar), 
             yleg = max(obj$y), xlim = range(xvar), ylim = NULL, 
             no.data = FALSE, color = TRUE, main = NULL, plot = TRUE)

Arguments

obj

a fitted gamlss object from fitting a gamlss continuous distribution

...

optionally more fitted GAMLSS model objects

xvar

the unique explanatory variable

cent

a vector with elements the % centile values for which the centile curves have to be evaluated

legend

whether a legend is required in the plot or not, the default is legent=TRUE

ylab

the y-variable label

xlab

the x-variable label

xleg

position of the legend in the x-axis

yleg

position of the legend in the y-axis

xlim

the limits of the x-axis

ylim

the limits of the y-axis

no.data

whether the data should plotted, default no.data=FALSE or not no.data=TRUE

color

whether the fitted centiles are shown in colour, color=TRUE (the default) or not color=FALSE

main

the main title

plot

whether to plot the centiles

Value

• Centile plots are produced for the different fitted models and the sample centiles below each centile curve are printed

Warning

This function is appropriate only when one continuous explanatory variable is fitted in the model

References

Rigby, R. A. and Stasinopoulos D. M.(2005). Generalized additive models for location, scale and shape, (with discussion),Appl. Statist., 54, part 3, pp 507-554. Stasinopoulos D. M., Rigby R.A. and Akantziliotou C. (2006) Instructions on how to use the GAMLSS package in R. Accompanying documentation in the current GAMLSS help files, (see also http://www.gamlss.org/).

See Also

gamlss, centiles , centiles.split

Examples

data(abdom)
h1<-gamlss(y~cs(x,df=3), sigma.formula=~cs(x,1),family=BCT, data=abdom)
h2<-gamlss(y~pb(x), sigma.formula=~pb(x), family=BCT, data=abdom )
centiles.com(h1,h2,xvar=abdom$x)
rm(h1,h2)