mixture {drc} | R Documentation |
'mixture' fits a concentration addition, Hewlett or Voelund model to data from mixture toxicity experiments.
mixture(object, model = c("CA", "Hewlett", "Voelund"), start, startm, control = drmc())
object |
object of class 'drc' corresponding to the model with freely varying EC50 values. |
model |
character string. It can be "CA", "Hewlett" or "Voelund". |
start |
optional numeric vector supplying starting values for all parameters in the mixture model. |
startm |
optional numeric vector supplying the lambda parameter in the Hewlett model or the eta parameters (two parameters) in the Voelund model. |
control |
list of arguments controlling constrained optimisation (zero as boundary), maximum number of iteration in the optimisation, relative tolerance in the optimisation, warnings issued during the optimisation. |
The function is a wrapper to drm
, implementing the models described in Soerensen et al. (2007).
See the paper for a discussion of the merits of the different models.
Currently only the log-logistic models are available. Application of Box-Cox transformation is not yet available.
An object of class 'drc' with a few additional components.
Christian Ritz
Soerensen, H. and Cedergreen, N. and Skovgaard, I. M. and Streibig, J. C. (2007) An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments, Environmental and Ecological Statistics, 14, 383–397.
The examples in acidiq
(the Hewlett model), glymet
(concentration addition)
and mecter
(the Voelund model).