R help - Apr 2003 - validate function in Design library does not work with small samples

Hi,

I am using the validate function in the design library
to get corrected Somer's Dxy for cox ph models.  When
my sample size is reduced from 300 to 150, the
function complains (length of dimnames[1] not equal to
array) and does not produce any results.  There are no
missing values in the data.  Any suggestions for a
work-around?

Thank you in Advance.
>
f.total=cph(Surv(fu,censor)~predictor+pred2+pred3,data=data,x=T,y=T,surv=T)
> set.seed(6)
> val.step=validate(f.total,B=155,bw=T)
                Backwards Step-down - Original Model

No Factors Deleted

Factors in Final Model

[1] pred2
.Random.seed: 1 -1021164091 1170333634 in .GlobalEnv 
Iteration:
1 2 3 4 5 6 7 Error in fit(NULL, y[train, , drop FALSE], iter = i, tol = tol,
...) :
        length of dimnames[1] not equal to array
extent
> val.step

On Fri, 25 Apr 2003 07:45:16 -0700 (PDT)
spok <spok_1 at yahoo.com> wrote:
> Hi,
> 
> I am using the validate function in the design library
> to get corrected Somer's Dxy for cox ph models.  When
> my sample size is reduced from 300 to 150, the
> function complains (length of dimnames[1] not equal to
> array) and does not produce any results.  There are no
> missing values in the data.  Any suggestions for a
> work-around?
> 
> Thank you in Advance.
> 
> >
> f.total=cph(Surv(fu,censor)~predictor+pred2+pred3,data=data,x=T,y=T,surv=T)
> > set.seed(6)
> > val.step=validate(f.total,B=155,bw=T)
> 
>                 Backwards Step-down - Original Model
> 
> No Factors Deleted
> 
> Factors in Final Model
> 
> [1] pred2
> .Random.seed: 1 -1021164091 1170333634 in .GlobalEnv 
> Iteration:
> 1 2 3 4 5 6 7 Error in fit(NULL, y[train, , drop > FALSE], iter = i, tol
= tol, ...) :
>         length of dimnames[1] not equal to array
> extent
> > val.step
In general it is best to contact the package maintainer directly.  Also, be sure
to give the output of typing the command

  version

and the version number of the package you are using.  For your problem please
run save( ) to save f.total and e-mail it to me as an attachment, then I'll
debug.  I'm glad you issued the set.seed command which should help me
replicate the problem.

Frank

---
Frank E Harrell Jr              Prof. of Biostatistics & Statistics
Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences
U. Virginia School of Medicine  http://hesweb1.med.virginia.edu/biostat