[R] Survival analysis
dwinsemius at comcast.net
Wed Feb 17 20:51:45 CET 2010
On Feb 17, 2010, at 1:54 PM, FishR wrote:
> Dear all
> I have a dataset examining the probability of a population surviving
> (calculated from a logistic regression) of a species over a 200yr
> The predictor variables are either continuous but non-normal (e.g.
> temperature, oxygen) or categorical (e.g. channelisation),
> unfortunately I
> also have a large amount of missing values.
> Year Decline Temperature Oxygen Channelisation
> 1800 0.947758115 36.6 NA NA
> 1801 0.946135961 25.2 NA NA
> 1802 0.944466388 28.5 NA NA
> 1803 0.942748196 35.5 NA NA
> 1804 0.940980166 33 NA NA
> 1805 0.93916106 30.2 NA NA
> truncated …
> 1999 0.028531339 10.5 NA 5
> 2000 0.027649801 8.4 NA 5
> I have been trying to run a Cox Proportional Hazards Model with the
> model<-coxph(Surv(Year, Decline) ~ Temperature + Oxygen +
> but keep getting an error message ‘Invalid status value’.
> Have I inputted the data in the wrong format or am I trying to run a
> unsuitable model?
The second. "Decline" in that coxph model would need to be a two level
variable, factor or integer, "event" or "censored".
You might get further if you described what data you had before you
"logistically" regressed it. (And is this a species of Galapagos
tortoises? I'm trying to figure out the 200 year time scale.)
> Any help would be greatly appreciated
David Winsemius, MD
West Hartford, CT
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