# [R] Clustering question \ dist(datmat)

Gabor Grothendieck ggrothendieck at gmail.com
Mon Mar 27 06:09:08 CEST 2006

```A distance matrix must be of class "dist".  Try

hclust(as.dist(df))

On 3/26/06, kumar zaman <statbataineh at yahoo.com> wrote:
> Hello everybody. I am trying to cluster circular data (data points which are angles), thus i can not use the "dist" function in "mclust" to generate my distance matrix, I am using the function " Dij = 0.5*( 1 - cos(theta_i - theta_j)). The thing is "hclust" will not accept this distance matrix, i tried to put it in a data frame, but again i get an error message saying " Error in if (n < 2) stop("must have n >= 2 objects to cluster") : argument is of length zero". The distance matrix "dist" producing is a lower triangular one, mine is a square matrix, which i think does not matter. My question how to make "hclust" process my distance matrix, what i am doing wrong. I am sure the problem is with the distance matrix format, Any suggestions are highly apprciated, the code below shows what i have done.
>
>  clust1<- as.vector(rvm(5,5,15))
> clust2<- as.vector(rvm(5,10,15))
> clust3<- as.vector(rvm(5,15,15))
> clust4<- as.vector(rvm(5,20,15))
> clust5<- as.vector(rvm(5,25,15))
> data1<- rbind(clust1,clust2,clust3,clust4,clust5)
> datmat<- matrix(data1,nrow=25,ncol=1,byrow=TRUE)
> circ.plot(datmat)
>    df<- array(dim=c(25,25))
>    for (i in 1:25){
>       for (j in 1:25){
>    df[i,j]<- 0.5*(1 - cos(datmat[i] - datmat[j]))
>          }
>          }
> hcA<-hclust(df,method="average")
>  ****************************************************
>  Ahmed
>  Florida
>
>
> ---------------------------------
>
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