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
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