[R] Cox PH Warning Message

[Neil Leonard]

This is the output. I think it means that there is a problem with 
project$pluralgpTriplet???

Neil

 > fm.CPH
Call:
coxph(formula = Surv(age_at_death, death) ~ project$pluralgp +
     project$yrborn + project$private + project$pcdead + project$mheight 
+
     project$ga2 + project$apgcode + project$apgar5 + project$VLBWgp +
     project$PEBW + project$LBWgp + project$LBWcat + project$totadm +
     project$totlos + project$sex + teen + project$DS + project$pcsborn +
     project$disadv + project$ecores + project$edoccu)


                                 coef exp(coef) se(coef)       z       p
project$pluralgpTwin       -0.509203     0.601  0.74415 -0.6843 4.9e-01
project$pluralgpTriplet           NA        NA  0.00000      NA      NA
project$yrborn1988-1992    -0.083348     0.920  0.22553 -0.3696 7.1e-01
project$private             0.260465     1.298  0.12384  2.1032 3.5e-02
project$pcdead             -0.058200     0.943  0.49418 -0.1178 9.1e-01
project$mheight             0.016361     1.016  0.01745  0.9378 3.5e-01
project$ga2                 0.104246     1.110  0.10162  1.0258 3.0e-01
project$apgcode4-7         -0.266885     0.766  0.50211 -0.5315 6.0e-01
project$apgcode1-3         -1.704620     0.182  1.12545 -1.5146 1.3e-01
project$apgar5             -0.427139     0.652  0.14099 -3.0296 2.4e-03
project$VLBWgp=>1500 grams  0.046203     1.047  0.65494  0.0705 9.4e-01
project$PEBW                0.015297     1.015  0.01356  1.1281 2.6e-01
project$LBWgp=>2500 grams  -0.257472     0.773  0.42496 -0.6059 5.4e-01
project$LBWcat             -0.222823     0.800  0.23938 -0.9308 3.5e-01
project$totadm              0.005836     1.006  0.01536  0.3800 7.0e-01
project$totlos              0.007342     1.007  0.00176  4.1664 3.1e-05
project$sexFemale          -0.016431     0.984  0.22803 -0.0721 9.4e-01
teen                        0.286282     1.331  0.34807  0.8225 4.1e-01
project$DSDown syndrome     1.193727     3.299  0.27227  4.3844 1.2e-05
project$pcsborn            -0.704743     0.494  0.75943 -0.9280 3.5e-01
project$disadv             -0.000573     0.999  0.00250 -0.2296 8.2e-01
project$ecores             -0.001588     0.998  0.00249 -0.6392 5.2e-01
project$edoccu              0.000590     1.001  0.00193  0.3054 7.6e-01

Likelihood ratio test=102  on 22 df, p=2.87e-12  n=2126 (1396 
observations deleted due to missing)
 >
On 16/10/2004, at 6:32 PM, Mayeul KAUFFMANN wrote:

> "Hi,
> Can anybody tell me what the message below means and how to overcome 
> it.
> Thanks,
> Neil
> Warning message:
> X matrix deemed to be singular; variable 2 in: coxph(Surv(age_at_death,
> death) ~ project$pluralgp + project$yrborn +  ........."
>
> Your 2nd covariate (yrborn) is colinear to the other covariates (or 
> nearly
> colinear). R drops it, but warns you. The results are OK.
>
> Mayeul KAUFFMANN
> Université Pierre Mendès France
> Grenoble
> France
>
>