[R] model fine, predict gives an error

[Antje Niederlein]

Anybody who can help me with this issue?




On 15 March 2011 14:15, Antje Niederlein <niederlein-rstat at yahoo.de> wrote:
> Hi there,
>
> I try to model some dose response curves (drc-package). In most cases
> it is fine but now I got some data which produces me the following
> error:
>
> load("drmData.RData")
> library(drc)
>
> drmObj <- drm(value ~ concentration, cmpd_respvar, data = drmData, fct = LL.4())
> predict(drmObj)
>
>>> Error in chol.default(0.99 * object$fit$hessian + 0.01 * diag(dim(object$fit$hessian)[1])) :
>  the leading minor of order 2 is not positive definite
> Error in resultMat[, 2] <- estSE : replacement has length zero
>
> Can anybody explain to me why the calculation of the dose response
> model works but the prediction fails? Anything I can do in this case?
>
> Antje
>