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str3
2013 Oct 03
2
SSweibull() : problems with step factor and singular gradient
SSweibull() : problems with step factor and singular gradient
Hello
I am working with growth data of ~4000 tree seedlings and trying to fit non-linear Weibull growth curves through the data of each plant. Since they differ a lot in their shape, initial parameters cannot be set for all plants. That’s why I use the self-starting function SSweibull().
However, I often got two error messages:
2007 Feb 15
1
bootcov and cph error
Hi all,
I am trying to get bootstrap resampled estimates of covariates in a Cox
model using cph (Design library).
Using the following I get the error:
> ddist2.abr <- datadist(data2.abr)
> options(datadist='ddist2.abr')
> cph1.abr <- cph(Surv(strt3.abr,loc3.abr)~cov.a.abr+cov.b.abr,
data=data2.abr, x=T, y=T)
> boot.cph1 <- bootcov(cph1.abr, B=100, coef.reps=TRUE, pr=T)
1 Error in oosl(f, matxv(X, cof), Y) : not implemented for cph models
>
Removing coef.reps argument works fine, but I really need the
coefficients if at all possible...