gamlss (version 4.2-4)

centiles: Plots the centile curves for a GAMLSS object

Description

This function centiles() plots centiles curves for distributions belonging to the GAMLSS family of distributions. The function also tabulates the sample percentages below each centile curve (for comparison with the model percentages given by the argument cent.) The function centiles.fan() plots a fan-chart of the centile curves. A restriction of the functions is that it applies to models with one explanatory variable only.

Usage

centiles(obj, xvar = NULL, cent = c(0.4, 2, 10, 25, 50, 75, 90, 98, 99.6), 
         legend = TRUE, ylab = "y", xlab = "x", main = NULL, 
         main.gsub = "@", xleg = min(xvar), yleg = max(obj$y), 
         xlim = range(xvar), ylim = range(obj$y), save = FALSE, 
         plot = TRUE, points = TRUE, pch = "+", col = "blue", 
         col.centiles = 1:length(cent) + 2, lty.centiles = 1, lwd.centiles = 1, ...)
centiles.fan(obj, xvar = NULL, cent = c(0.4, 2, 10, 25, 50, 75, 90, 98, 99.6), 
         ylab = "y", xlab = "x", main = NULL, main.gsub = "@", 
         xleg = min(xvar), yleg = max(obj$y), xlim = range(xvar), 
         ylim = range(obj$y), points = FALSE,  median = TRUE,  pch = "+", 
         col = "blue", 
         colors = c("cm", "gray", "rainbow", "heat", "terrain", "topo"), ...)

Arguments

obj

a fitted gamlss object from fitting a gamlss distribution

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

main

the main title here as character. If NULL the default title "centile curves using NO" (or the relevant distributions name) is shown

main.gsub

if the main.gsub (with default "@") appears in the main title then it is substituted with the default title.

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

save

whether to save the sample percentages or not with default equal to FALSE. In this case the sample percentages are printed but are not saved

plot

whether to plot the centiles. This option is useful for centile.split

pch

the character to be used as the default in plotting points see par

col

plotting colour see par

col.centiles

Plotting colours for the centile curves

lty.centiles

line type for the centile curves

lwd.centiles

The line width for the centile curves

colors

the different colour schemes to be used for the fan-chart. The following are available c("cm","gray", "rainbow", "heat", "terrain", "topo"),

points

whether the data points should be plotted, default is TRUE for centiles() and FALSE for centiles.fan()

median

whether the median should be plotted (only in centiles.fan())

...

for extra arguments

Value

• A centile plot is produced and the sample centiles below each centile curve are printed (or saved)

Warning

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

Details

Centiles are calculated using the fitted values in obj and xvar must correspond exactly to the predictor in obj to plot correctly. col.centiles, lty.centiles and lwd.centiles may be vector arguments and are recycled to the length cent if necessary.

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/). Stasinopoulos D. M. Rigby R.A. (2007) Generalized additive models for location scale and shape (GAMLSS) in R. Journal of Statistical Software, Vol. 23, Issue 7, Dec 2007, http://www.jstatsoft.org/v23/i07.

See Also

gamlss, centiles.split , centiles.com

Examples

data(abdom)
h<-gamlss(y~pb(x), sigma.formula=~pb(x), family=BCT, data=abdom) 
# default plot
centiles(h,xvar=abdom$x)
# control of colours and lines
centiles(h, xvar=abdom$x,  col.cent=c(2,3,4,5,1,5,4,3,2,1), 
              lwd.cent=c(1,1,1,1,2,1,1,1,1))
#Control line types
centiles(h, xvar=abdom$x,  col.cent=1, cent=c(.5,2.5,50,97.5,99.5), 
              lty.centiles=c(3,2,1,2,3),lwd.cent=c(1,1,2,1,1))
# control of the main title
centiles(h, xvar=abdom$x,  main="Abdominal data 
 @")
# the fan-chart
centiles.fan(h,xvar=abdom$x, colors="rainbow")
rm(h)