rm(list=ls())  
ex11.3 <- read.table("例11-1.txt", head=TRUE, fileEncoding="utf8")  
fit <- cmdscale(ex11.3, k=2, eig = TRUE)  
#特征根  
round(fit$eig)  
#a12  
round(sum(fit$eig[1:2]) / sum(abs(fit$eig)) , 3)  
#a22  
round(sum((fit$eig[1:2])^2) / sum((fit$eig)^2), 3)   
round(fit$points)  





