# [R] ifelse command

Carlos J. Gil Bellosta cgb at datanalytics.com
Sat Jul 22 21:10:20 CEST 2006

```Dear Xin,

Although I have no idea what your function does, I believe it would be
"formally" correct in the following way:

foo <- 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(y>0 & x1>0 & x2==1) return( lgamma(y+p)+p*(log(p)-log(mu
+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p) )
if(y>0 & x1>0 & x2==2) return( lgamma(y+p)+p*(log(p)-log(mu
+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p) )
if(y>0 & x1>0 & x2==3) return( lgamma(y+p)+p*(log(p)-log(mu
+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p) )

return( "what then?" )
}

Please, compare your code to mine. You will discover more than one error
in your code. See also where the if() parenthesis closes. I do not
believe your else's are necessary within a function. See also that the
code after your ifs is always the same.

Sincerely,

Carlos J. Gil Bellosta
http://www.datanalytics.com
http://www.data-mining-blog.com

El sáb, 22-07-2006 a las 13:25 +0100, Xin escribió:
> Dear:
>
>    I try to revise the maximum likelihood function below using something constrains. But it seems something wrong with it.  Becasue R would not allow me to edit the function like this. It is very appreciate if you can help.
>
> 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(y>0 & x1>0 & x2==1,
>
> L<-lgamma(y+p)+p*(log(p)-log(mu+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p)
>
> )
>
> else
>
> if(y>0 & x1>0 & x2==2,
>
> L<-lgamma(y+p)+p*(log(p)-log(mu+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p)
>
> )
>
> else
>
> if(y>0 & x1>0 & x2==3,
>
> L<-lgamma(y+p)+p*(log(p)-log(mu+p))+y*(log(mu)-log(mu+p))-lfactorial(y)-lgamma(p)
>
> )
>
> else
>
> L
>
> }
>
> Thanks a lot!
>
> Xin Shi
>
> 	[[alternative HTML version deleted]]
>
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```