[R] model fine, predict gives an error

From: Antje Niederlein <niederlein-rstat_at_yahoo.de>
Date: Tue, 15 Mar 2011 14:15:16 +0100

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:


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?


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