seg: Specifying a segmented term in the segreg formula
In segmented: Regression Models with Break-Points / Change-Points Estimation (with Possibly Random Effects)

View source: R/seg.r

seg	R Documentation

Specifying a segmented term in the segreg formula

Description

Function used to define the segmented term within the segreg formula. The function simply passes relevant information to proper fitter functions.

Usage

seg(x, psi = NA, npsi = 1, est = NA, R = NA, fixed.psi = NULL, by = NULL, f.x = I)

Arguments

`x`	The segmented (numeric) covariate
`psi`	Possible starting value(s) for the breakpoint(s). If omitted, `npsi` has to be specified.
`npsi`	The number of breakpoints to estimate. Default `npsi=1`.
`est`	Possible vector (of length equal to `npsi+1`) of 0/1 to indicate whether the slopes have to be estimated of fixed to zero. If `NA`, default, means all ones, namely every slope has to be estimated. Consecutive zeroes are not allowed.
`R`	Matrix to constrain the slopes. If provided, it overwrites the matrix coming from the specification of `est`
`fixed.psi`	Possible fixed breakpoint values. These will be accounted for in addition to the estimated ones; `slope` and `plot.segmented` will account for them correctly.
`by`	A possible factor meaning an interaction with the segmented term. It means that a different segmented relationship is fitted within each category.
`f.x`	an optional function meaning a function to apply to the covariate before fitting

Details

The function is used within segreg to 'build' information about the segmented relationships to fit.

Value

The function simply returns the covariate with added attributes relevant to segmented term

Note

If any value is provided in fix.psi, the corresponding slope difference coefficient will be labelled by *.fixed.*. The slope function will compute the 'right' slopes also accounting for the fixed breakpoints.