On 2011-06-16 17:20, B. Santos wrote:
> Hello everyone,
>
> I am trying to use rpy2 to estimate the parameters of a specified function.
> But I am failing miserable to understand how I can do this using rpy2. I
> have the following R code: alphabeta<-function(alphabeta,x,dicerAcc) {
> alpha<-alphabeta[1]
> beta<-alphabeta[2]
> if (any(alphabeta<0))
> return(NA)
> sum((alpha*log(beta) + lgamma(alpha + x) + x * log(dicerAcc) -
> lgamma(alpha) - (alpha + x) * log(beta+dicerAcc) - lfactorial(x))[dicerAcc
>> noiseT]) ab<- optim(c(1,100), alphabeta, control=list(fnscale=-1), x =
> x, dicerAcc = dicerAcc)$par
>
> Is there anyway to do this. I would imagine the easy way would be to
> import
> the function from R but I imagine that means I would have to create a
> package just for the function which is less than ideal.
>
You can just parse and evaluate a string as R code as an anonymous R
function.
http://rpy.sourceforge.net/rpy2/doc-2.2/html/rinterface.html#parsing-and-evaluating-r-code
and then use base.eval().
You can also consider writing your cost function in Python:
http://rpy.sourceforge.net/rpy2/doc-2.2/html/rinterface.html#calling-python-functions-from-r
HTH,
L.
> Looking forward to your suggestion. Thank you very much in advance,
> Bruno Santos
>
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