[RsR] library cox robust : weights?

[Elisabetta Mattiolo]

I'm a italian student and I use R for my final degree thesis ... I want
study a Robustly Proportional Hazards (Bednarski's teory) for a dataset
of medical result. 
I have exstimate with library coxrobust a coxr model (exponential
weights)

> s=Surv(survival,status)

site , cyto5.6 and zeb1 are my esplicative variables so the model is:

> exp=coxr(formula = s ~ site + cyto5.6 + zeb1, data = IHC, trunc =
0.95, f.w= "exp" , singular.ok = TRUE, model = FALSE)

with plot(exp) I can see 5 graphs 
- the firs shows the standardizzed survival differences : one with Cox
model, and one green with Kaplan -Meir stimator 
-other four show the same differences for four strata, defined by the
quartiles of the estimated linear predictor. 

But my problem is the I want a graphic the robust exponential weight
(log trasformed) versus case number for the dataset..
If I ask R about weight of the model exp: 
> exp$weights
NULL
If I write 
> plot(exp$weights)
Error in plot.window(...) : 'xlim' devono essere finiti
Inoltre: Warning messages:
1: In min(x) : no non-missing arguments to min; returning Inf
2: In max(x) : no non-missing arguments to max; returning -Inf
3: In min(x) : no non-missing arguments to min; returning Inf
4: In max(x) : no non-missing arguments to max; returning -Inf


Can you help me?
Thanks and best regards

Elisabetta 


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