## 新的text mining package textir in R 

## 列出前20個高變異的tdifd詞
## 有提供tdidf函數可計算tdidf矩陣

library(textir)
data(we8there)
## 20 high-variance tf-idf terms
colnames(we8thereCounts)[
order(-sdev(tfidf(we8thereCounts)))[1:20]]