This function calculates the hazard ratio (HR) from an estimated model in a WCE object to compare two scenarios of timedependent exposures.
1 
x 
A WCE object. 
vecnum 
A vector of timedependent exposures corresponding to a scenario of interest (numerator of the HR). 
vecdenom 
A vector of timedependent exposures corresponding to a scenario for the reference category (denominator of the HR). 
allres 
Logical. If FALSE, prints the results using the best model from the WCE object, i.e. among the models fitted with the different numbers of interior knots requested by nknots, based on AIC or BIC as specified in the 
Both vecnum
and vecdenom
need to be of the same length as the weight function cutof
argument used in the call to WCE. The hazard ratio computed by HR.WCE
corresponds to the ratio of the weighted cumulative exposures for the scenario of interest (vecnum) and the reference scenario (vecdenom). It corresponds to equation (8) of Sylvestre and Abrahamowicz (2009).
Returns one or several hazard ratios. Inference may be obtained by bootstrap and has to be coded separately (please see WCE
for an example).
MariePierre Sylvestre
mariepierre.sylvestre@umontreal.ca
Sylvestre MP, Abrahamowicz M. Flexible modeling of the cumulative effects of timedependent exposures on the hazard. Stat Med. 2009 Nov 30;28(27):343753.
1 2 3 4 5 6 7 8  wce < WCE(drugdata, "Cox", 1, 90, constrained = "R", id = "Id", event = "Event",
start = "Start", stop = "Stop", expos = "dose",
covariates = c("age", "sex"))
# Exposed at a dose of 1 (constant) vs. unexposed over the time window of 90 days
scenario1 < rep(1, 90)
scenario2 < rep(0, 90)
HR.WCE(wce, vecnum = scenario1, vecdenom = scenario2)

Questions? Problems? Suggestions? Tweet to @rdrrHQ or email at ian@mutexlabs.com.
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