hi isabel,
You have to decide if focus is on the survival curves or hazards..
Crossing hazards do not imply crossing survival curves
If you are dealing with crossing hazards, and you are interested in
testing for an effect of a covariate (presumably with a crossing hazard
effect), then a standard Cox model framework based on the martingale
representation "(start, stop, event)" (rather than "(time, event)") will
suffice
Finally, if you are interested in estimating the crossing point you
could have a look to the package flexCrossHaz (currently in the
Archive.. Let me know if you are interested in becoming maintainer..:-)
)
http://cran.r-project.org/src/contrib/Archive/flexCrossHaz/
best,
vito
Il 05/07/2012 12.37, Isabel Borges ha scritto:
Hi
I want to compare the survival curves in two groups. Because the hazards are
not proportional (the curves cross) the log rank test or Cox proportional
hazard test are not suitable. How should such curves be compared? Comands
are welcome....
Thanks in advance
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====================================
Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Università di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 23895240
fax: 091 485726
http://dssm.unipa.it/vmuggeo
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