[R] Estimating Daily Survival

[Bret Collier]

R Users,
I was wondering if someone might point me in the right direction.  I am using a Cox model (survival package) to evaluate survival of pen-reared birds (time to event data collected daily) and I have been trying to determine how I can estimate a 'daily' survival rate and std error from the results of a Cox model?  

Using survfit (see input data below) I computed the predicted survivor function for a Cox model, but I have been unable to figure out how to estimate a 'daily' survival rate for an average individual?  Should I be looking at survexp?  Any suggestions would be appreciated.

Thanks,
Bret


brettest1<-coxph(Surv(Entry, Exit, Fate)~Sex , data=mydat)
brettest1

      coef exp(coef) se(coef)     z    p
Sex -0.503     0.605    0.524 -0.96 0.34

Likelihood ratio test=0.92  on 1 df, p=0.337  n= 19 


> survfit(brettest1)$surv
 [1] 0.9502716 0.9010356 0.8508737 0.7996929 0.7473818 0.6957615 0.5872297 0.5324263 0.4756545
[10] 0.4201535 0.3547775 0.2916481 0.2189030 0.1374015

>mydat
       ID Year Dayrelease Agerelease Survivorship Entry Exit Fate Sex
1   16240 1996        205         95          164   205  369    1   0
2   16319 1996        205         88          140   205  345    1   0
3   16378 1996        248        108          100   248  348    1   0
4   20383 1996        241         98          204   241  445    1   0
5   16324 1996        219         90          227   219  446    1   0
6   16327 1996        219         90          497   219  716    1   0
7   20373 1996        241        114          413   241  654    1   0
8   20374 1996        241        111          211   241  452    1   0
9   16241 1996        205         95          234   205  439    1   1
10  16321 1996        219         90          118   219  337    1   1
11  16323 1996        219         90          180   219  399    1   1
12  20375 1996        241        103          268   241  509    1   1
13  20384 1996        241         98          299   241  540    1   1
14  20390 1996        241         93          204   241  445    1   1
15  20393 1996        241         88          208   241  449    1   1
16  16313 1996        248        122          512   248  760    0   1
17  20378 1996        241        103          236   241  477    0   1
18  20381 1996        241        101          329   241  570    0   1
19  16328 1996        219         90          224   219  443    0   1


platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    2.1            
year     2005           
month    12             
day      20             
svn rev  36812          
language R