You need to read the help page for optimize. Again, if you already have ;-)
The error message >Error in optimize(llik, init.params = F) : element 1 is empty; > the part of the args list of 'min' being evaluated was: > (interval)#### is telling you that the parameter (interval) required by optimise in the absence of a specified min and max is empty. And if you look at your code you will see that that is because you have not provided it.... There are other problems: Optimize requires a function taking _one_ parameter to optimise and an interval to optimise over, or alternatively a maximum and a minimum. You have provided no interval, max or min (which is why it went looking for interval) and you have fed it a function taking two parameters, both of which you want optimised. You have also given it initial parameters (?) as a named parameter which it can't recognise - it's not one of the named arguments to optimize - so optimize will try to pass that to the function being optimised. That will fail if it ever gets there because _that_ doesn't use a parameter called init.params either. I'm not clear what you wanted init.params to do but at a rough guess you had in mind a function for which init.params is the initial parameter vector and if FALSE is guessed at. optmize() is not that function. Perhaps you meant to use optim - which does two-parameter optimisation - but you _will_ need to specify a starting vector as that doesn't take an init.params argument either. As an alternative, you could use something like nls which takes a self-starting function argument which generats its own initial values, but you'll have to create the self-starting function yourself (see ?selfStart) > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Edward Bowora > Sent: 01 July 2011 01:46 > To: r-help > Subject: [R] Help fix last line of my optimization code > > Hi > > I need help figure out how to fix my code. > > When I call into R > >optimize(llik,init.params=F) > I get this error message > ####Error in optimize(llik, init.params = F) : element 1 is empty; > the part of the args list of 'min' being evaluated was: > (interval)#### > > > My data and my code looks like below. > > > R_j R_m > 0.002 0.026567296 > 0.01 0.003194435 > . . > . . > . . > . . > 0.0006 0.010281122 > > a=read.table("D:/ff.txt",header=T) > attach(a) > llik=function(R_j,R_m) > #The parameters al_j, au_j, b_j , > and sigma_j need to be estimated and there are no initial > estimates to them. > if(R_j< 0) > { > > LF=sum[log(1/(2*pi*(sigma_j^2)))-(1/(2*(sigma_j^2))*(R_j+al_j- > b_j*R_m))^2] > }else if(R_j>0) > { > > LF=sum[log(1/(2*pi*(sigma_j^2)))-(1/(2*(sigma_j^2))*(R_j+au_j- > b_j*R_m))^2] > }else > { > > LF=sum[(log(pnorm((au_j-b_j*R_m)/sigma_j)-pnorm((al_j-b_j*R_m) > /sigma_j)))] > } > optimize(llik,init.params=F) > Error in optimize(llik, init.params = F) : element 1 is empty; > the part of the args list of 'min' being evaluated was: > (interval) > > Thank you > > Edward > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ******************************************************************* This email and any attachments are confidential. Any use...{{dropped:8}} ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
