Problem in log

yes, log of negative number is undefined and R also do the same and produces
NaNs. Here I want to reject the value of exp(-alpha*d^(-beta)) when greater
than 1, and want to run the loop otherwise.
Thanks

On Tue, Nov 29, 2011 at 6:48 PM, Sarah Goslee <sarah.goslee at gmail.com>
wrote:

Here p[i] <- 1 - exp(-alpha*d^(-beta))> so, ?log(p[i]) produces NaNs
when exp(-alpha*d^(-beta)) is greater than 1.> How can I remove it.After
generating the out put we can omit it, but the> problem is different.

Wait... you're complaining that you can't take the natural log of a
negative
number in R?

You can't do that anywhere. What do you expect to happen? The log of a
negative number IS NaN.

Sarah
On Tue, Nov 29, 2011 at 6:28 PM, Gyanendra Pokharel
<gyanendra.pokharel at gmail.com> wrote:

I have following code:
loglikelihood <- function(alpha,beta= 0.1){
? ?loglh<-0
? ?d<-0
? ?p<-0
? ?k<-NULL
? ?data<-read.table("epidemic.txt",header = TRUE)
? ?attach(data, warn.conflicts = F)
? ?k <-which(inftime==1)
? ?d <- (sqrt((x-x[k])^2+(y-y[k])^2))^(-beta)
? ?p<-1 - exp(-alpha*d)
? ?for(i in 1:100){
? ? ? ?if(i!=k){
? ? ? ? ? ?if(inftime[i]==0){
? ? ? ? ? ? ? ?loglh<-loglh +log(1-p[i])
? ? ? ? ? ?}
? ? ? ? ? ?if(inftime[i]==2){
? ? ? ? ? ? ? ?loglh<-loglh + log(p[i])
? ? ? ? ? ?}
? ? ? ?}
? ?}
? ?return(loglh)
}
Here p[i] <- 1 - exp(-alpha*d^(-beta))
so, ?log(p[i]) produces NaNs when exp(-alpha*d^(-beta)) is greater than
1.
How can I remove it.After generating the out put we can omit it, but the
problem is different.

On Tue, Nov 29, 2011 at 5:22 PM, Gyanendra Pokharel <
gyanendra.pokharel at gmail.com> wrote:

No, that,s not a problem Michael,
I have following code:
loglikelihood <- function(alpha,beta= 0.1){
? ? loglh<-0
? ? d<-0
? ? p<-0
? ? k<-NULL
? ? data<-read.table("epidemic.txt",header = TRUE)
? ? attach(data, warn.conflicts = F)
? ? k <-which(inftime==1)
? ? d <- (sqrt((x-x[k])^2+(y-y[k])^2))^(-beta)
? ? p<-1 - exp(-alpha*d)
? ? for(i in 1:100){
? ? ? ? if(i!=k){
? ? ? ? ? ? if(inftime[i]==0){
? ? ? ? ? ? ? ? loglh<-loglh +log(1-p[i])
? ? ? ? ? ? }
? ? ? ? ? ? if(inftime[i]==2){
? ? ? ? ? ? ? ? loglh<-loglh + log(p[i])
? ? ? ? ? ? }
? ? ? ? }
? ? }
? ? return(loglh)
}
Here p[i] <- 1 - exp(-alpha*d^(-beta))
so, ?log(p[i]) produces NaNs when exp(-alpha*d^(-beta)) is greater than
1.
How can I remove it.After generating the out put we can omit it, but
the
problem is different.

--
Sarah Goslee
http://www.functionaldiversity.org