prettyNum
を使うと便利。
コード
x <- 1:10 * 1000000
prettyNum(x, big.mark=",", big.interval=3, scientific=FALSE)
結果
[1] " 1,000,000" " 2,000,000" " 3,000,000" " 4,000,000" " 5,000,000"
[6] " 6,000,000" " 7,000,000" " 8,000,000" " 9,000,000" "10,000,000"
参考: http://stat.ethz.ch/R-manual/R-devel/library/base/html/formatc.html