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Martyn
Thanks for the help the function works. I used lower.tri() in 
package(ape) to extract the Lower triangular portion of the matrix since 
thats what I needed the func looks like this
Thanks to all who contributed-the function works.

IED <- function(risk) {
n <- length(risk)
mrisk <- matrix(rep(risk,n),ncol=n,byrow=T)
diff <- abs(risk - mrisk)
library(base)
keep <- lower.tri(diff)
c(diff)[c(keep)]
}

Thanks
Oarabile


Martyn Byng wrote:

> Hi,
>
> I am assuming this is in either R or SPlus ?
>
> In both of these packages it is best to avoid doing loops where 
> possible, something along the lines of
>
> IED <- function(risk) {
> n <- length(risk)
> mrisk <- matrix(rep(risk,n),ncol=n,byrow=T)
> diff <- abs(risk - mrisk)
> keep <- matrix(T,nrow=n,ncol=n)
> diag(keep) <- F
> c(diff)[c(keep)]
> }
>
> seems to work.
>
> In your code I think it is the line
>
> Difference<-Difference[-c(1:j)]
>
> that is at fault, this drops the first j elements from Difference, 
> which is Difference[j] - Difference[j] only for j = 1
>
> Hope that helps
>
> Martyn
>
> Oarabile Molaodi wrote:
>
>>> I'm trying to write a function that takes a vector of length n  and 
>>> then takes the first value of the vector i.e j=1 and forms a new 
>>> vector of length n (i.e replicate the first value n times). This 
>>> function will then calculate the absoulte difference of the original 
>>> vector and the new vector and store the results omitting the 
>>> difference between the value and itself. This function should be 
>>> able to repeat the procedure for each of the j's i.e j=2 to n. The 
>>> results should all be stored together. Below is  what I've tried so 
>>> far but it seems to work only for j=1 .
>>>
>>> Your help will be highly appreciated.
>>
>>
>>
>>
>>> IED<-function(risk){
>>> n<-length(risk)
>>> i<-c(1:n)
>>> Diff<-numeric()
>>> for(j in 1:n){
>>> relrisk<-risk
>>> relrisk[i]<-relrisk[j]
>>> Difference<-abs(risk-relrisk)
>>> Difference<-Difference[-c(1:j)]
>>> Difference<-append(Diff,Difference)
>>> return(Difference)
>>> }
>>> }
>>>
>>>
>>> Oarabile
>>>
>>
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