attrassign: Create new-style "assign" attribute

Description Usage Arguments Details Value See Also Examples

Description

The "assign" attribute on model matrices describes which columns come from which terms in the model formula. It has two versions. R uses the original version, but the alternate version found in S-plus is sometimes useful.

Usage

1
2
3
4
## Default S3 method:
attrassign(object, tt,...)
## S3 method for class 'lm'
attrassign(object,...)

Arguments

object

model matrix or linear model object

tt

terms object

...

ignored

Details

For instance consider the following

1
2
    survreg(Surv(time, status) ~ age + sex + factor(ph.ecog), lung)
  

R gives the compact for for assign, a vector (0, 1, 2, 3, 3, 3); which can be read as “the first column of the X matrix (intercept) goes with none of the terms, the second column of X goes with term 1 of the model equation, the third column of X with term 2, and columns 4-6 with term 3”.

The alternate (S-Plus default) form is a list

1
2
3
4
5
       $(Intercept)     1
       $age             2
       $sex             3
       $factor(ph.ecog) 4 5 6
     

Value

A list with names corresponding to the term names and elements that are vectors indicating which columns come from which terms

See Also

terms,model.matrix

Examples

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
formula <- Surv(time,status)~factor(ph.ecog)
tt <- terms(formula)
mf <- model.frame(tt,data=lung)
mm <- model.matrix(tt,mf)
## a few rows of data
mm[1:3,]
## old-style assign attribute
attr(mm,"assign")
## alternate style assign attribute
attrassign(mm,tt)

survival documentation built on April 26, 2021, 9:06 a.m.