## save the distance matrix
dist.prices <- dist(prices)

### simple linkage
model.singleLinkage <- hclust(dist.prices, method = "single")
plot(model.singleLinkage)
cutree(model.singleLinkage, k = 3)
plot(model.singleLinkage)
rect.hclust(model.singleLinkage, k = 3, border = "red")

### complete linkage
model.completeLinkage <- hclust(dist.prices, method = "complete")
plot(model.completeLinkage)
rect.hclust(model.completeLinkage, k=3, border="red") 

### average linkage
model.averageLinkage <- hclust(dist.prices, method = "average")
plot(model.averageLinkage)
rect.hclust(model.averageLinkage, k=3, border="red") 

### Ward's model
model.Ward <- hclust(dist.prices, method = "ward.D")
plot(model.Ward)
rect.hclust(model.Ward, k=3, border="red")