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??

Thanks

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