[R] X matrix deemed to be singular;

[Gad Abraham]

Michele Santacatterina wrote:
> Hello,
> 
> i'm tring to use a cox's model for a survival analysis. I have a dataset,
> this is a part:
> 
>    VOD SESSO fonte_sct     donor     RT_CGY STATOBMT TEMPO morto
> 1     0     F       mid                related      1200
> CP                65        1
> 2     0     M      mid                                 1200
> 2RC             5281      0
> 3     0     M      mid               unrelated   1200      1RC
> 218       0
> 4     0     M      per                unrelated   1200      2RC
> 484        0
> 5     0     F       mid                                  1200
> 1RC             302        1
> 6     0     M      mid                related      1200      1RC
> 1235        0
> 
> 
> but when i try this command i have a warning:
> 
>> fit = coxph( Surv(TEMPO,morto==1)~ VOD + SESSO + fonte_sct + donor +
> RT_CGY + STATOBMT)
> Warning message:
> In coxph(Surv(TEMPO, morto == 1) ~ VOD + SESSO + fonte_sct + donor +  :
>   X matrix deemed to be singular; variable 10 14 15 18 20 21 22 24 25 26
> 
> 
> why??? anyone know the solution of this??
> 

Perhaps your some of your variables are very highly correlated with each 
other, leading to a singular covariance matrix?

-- 
Gad Abraham
Dept. CSSE and NICTA
The University of Melbourne
Parkville 3010, Victoria, Australia
email: gabraham at csse.unimelb.edu.au
web: http://www.csse.unimelb.edu.au/~gabraham