untangle.specials {survival4} | R Documentation |
untangle.specials(tt, special, order=1)
tt |
a terms object.
|
special |
the name of a special function, presumably used in the terms object. |
order |
the order of the desired terms. If set to 2, interactions with the special function will be included. |
vars |
a vector of variable names, as would be found in the data frame, of the specials. |
terms |
a numeric vector, suitable for subscripting the terms structure, that indexes the terms in the expanded model formula which involve the special. |
a list with two components:
# This is code from within the coxph program, m is the data frame and TT # the terms structure for the formula. We wish to exclude first order # strata() terms from the final X matrix, and also to extract these terms # to a second data frame TT <- terms(formula, specials='strata') temp <- untangle.specials(TT, 'strata') if (length(temp$vars)) { X <- model.matrix( TT[-temp$terms], m) m.strat <- m[temp$vars] } else X <- model.matrix(TT, m)