계량적MDS와 비계량적MDS 예시

##### 계량적MDS : cmdscale사례

library(MASS)

head(eurodist)

str(eurodist)

eurodist

# cmdscale() : 2차원으로 21개 도시들을 매핑

loc<-cmdscale(eurodist)

x<-loc[,1]

y<- -loc[,2] # 북쪽도시를 상단에 표시하기 위해 부호를 바꾼 것

plot(x, y, type="n", asp=1, main="Metric MDS") # asp=x축의 단위

text(x, y, rownames(loc), cex=0.7)

abline(v=0, h=0, lty=2, lwd=0.5) # v=x축; h=y축; lty=선타입; lwd=선굵기

##### 비계량적MDS : isoMDS와 sammon사례

library(MASS)

data(swiss)

swiss

head(swiss)

# iosMDS

swiss.x<-as.matrix(swiss[,-1])

swiss.dist<-dist(swiss.x) # 열과 데이터매트릭스간의 거리

swiss.mds<-isoMDS(swiss.dist) 

plot(swiss.mds$points, type="n")

text(swiss.mds$points, labels=as.character(1:nrow(swiss.x)))

abline(v=0, h=0, lty=2, lwd=0.5)

?isoMDS

# sammon

swiss.x<-as.matrix(swiss[,-1])

swiss.sammon<-sammon(dist(swiss.x))

plot(swiss.sammon$points, type="n")

text(swiss.sammon$points, labels=as.character(1:nrow(swiss.x)))

abline(v=0, h=0, lty=2, lwd=0.5)