centroide = function (X, col.especimes)    
{
M = X[,sapply(X,is.numeric)]
cent=apply(M,2,mean)
cent
p<-dim(M)[1]
size<-sqrt(sum(apply(M,2,var))*(p-1))
cent.size=list("centroid_size"=size,"scaled"=M/size)
cent.size 
especime_x<-tapply(x,col.especimes,mean)
especime_y<-tapply(y,col.especimes,mean)
especime_z<-tapply(z,col.especimes,mean)
cent.esp<-rbind(especime_x,especime_y,especime_z) 
cent.esp                                                                   
return(list(cent, cent.size, cent.esp))
}