Re: [R] Why the contrain does not work for selecting a particular range of data?

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Sun 23 Jul 2006 - 22:14:33 EST

On 7/23/2006 4:07 AM, Xin wrote:
> Dear:
>
> Continuing the issue of 'ifelse'! I selecting the data whose 'x2'=1 for maximizing likelihood. I used two way to do this but the results are different.

In the first case you used ifelse(), in the second you used if(). They behave differently: ifelse() evaluates all tests in a vector, if() only evaluates one. You probably want ifelse() in both cases.

Duncan Murdoch

>
> 1.Way one I use the data for x2=1 and run the program. It works for me. Tthe program is described as below:
> function (parameters,y1,x11)
> {
> p<-parameters[1]
> alpha1<-parameters[2]
> beta1<-parameters[3]
> delta1<-parameters[4]
> lamda1<-parameters[5]
>
> mu<-alpha1*((x11)^beta1)*exp(-delta1*(x11^lamda1))
>
> ifelse(y1>0|x11>0,
>
> L<-lgamma(y1+p)+p*(log(p)-log(mu+p))+y1*(log(mu)-log(mu+p))-lfactorial(y1)-lgamma(p)
>
> ,Inf)
>
> L
>
> }
>
> This is working for me.
>
> 2 Way two: I select the data whose x2=1 in the whole range of data. It works but it is not right comparing the value of MLE. the program is:
> function (parameters,y,x1,x2)
>
> {
>
> p<-parameters[1]
>
> alpha1<-parameters[2]
>
> beta1<-parameters[3]
>
> delta1<-parameters[4]
>
> alpha2<-parameters[5]
>
> mu<-alpha1*((x1)^beta1)*exp(-delta1*(x1^alpha2))
>
> if(x1>0 & x2==1)
>
> {
>
> L<-lgamma(y+p)+p*(log(p)-log(mu+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p)
>
> }
>
>
>
> L
>
> }
>
> The reason why I edit the program by the second way is I want to use one program for getting results of the different range of data.
>
> Anyone can help? Please!
>
> Thanks!
>
>
>
> Xin Shi
>
>
>
> My Estimation function for way two is :
>
> function (parameters, y, x1,x2)
>
> {
>
> nx1 <- length(x1);
>
> nx2 <- length(x2);
>
> ny <- length(y);
>
> x1 <- matrix(x1,nrow=nx1,ncol=1);
>
> x2 <- matrix(x2,nrow=nx2,ncol=1);
>
> y <- matrix(y,nrow=ny,ncol=1);
>
> ##Likelihood
>
> ##----------
>
> Lvec <- matrix(0,nrow=nx1,ncol=1)
>
> for (i in 1:ny)
>
> {
>
> Lvec[i] <- nb_L3(parameters, y[i],x1[i],x2[i])
>
> LL <- -sum(Lvec)
>
> }
>
> LL
>
> }
>
> [[alternative HTML version deleted]]
>
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R-help@stat.math.ethz.ch 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. Received on Sun Jul 23 22:21:13 2006

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