segmented (version 0.5-2.1)

broken.line: Fitted values for segmented relationships

Description

Given a segmented model (typically returned by a segmented method), broken.line computes the fitted values (and relevant standard errors) for each `segmented' relationship.

Usage

broken.line(ogg, term = NULL, link = TRUE, interc=TRUE, se.fit=TRUE)

Arguments

ogg

A fitted object of class segmented (returned by any segmented method).

term

Three options. A list (whose name should be one of the segmented covariates) including values for which segmented predictions should be computed. A character meaning the name of any segmented covariate in the model. NULL if the model includes a single segmented covariate.

link

Should the predictions be computed on the scale of the link function? Default to TRUE.

interc

Should the model intercept be added? (provided it exists).

se.fit

If TRUE also standard errors for predictions are returned.

Value

A 2-component (if se.fit=TRUE) list representing predictions and standard errors for the segmented covariate values.

Details

If term=NULL or term is a valid segmented covariate name, predictions for each segmented variable are the relevant fitted values from the model. If term is a (correctly named) list with numerical values, predictions corresponding to such specified values are computed. If link=FALSE and ogg inherits from the class "glm", predictions and standard errors are returned on the response scale. The standard errors come from the Delta method. Argument link is ignored whether ogg does not inherit from the class "glm".

See Also

segmented, predict.segmented, plot.segmented

Examples

set.seed(1234)
z<-runif(100)
y<-rpois(100,exp(2+1.8*pmax(z-.6,0)))
o<-glm(y~z,family=poisson)
o.seg<-segmented(o,seg.Z=~z,psi=.5)
plot(z,y)
points(z,broken.line(o.seg,link=FALSE)$fit,col=2) #just to illustrate, use plot.segmented