合并（rbind）數(shù)據(jù)幀并使用原始數(shù)據(jù)幀的名稱創(chuàng)建列我有幾個(gè)數(shù)據(jù)框，我想按行組合。在生成的單個(gè)數(shù)據(jù)框中，我想創(chuàng)建一個(gè)新變量，用于標(biāo)識(shí)觀察來(lái)自哪個(gè)數(shù)據(jù)集。# original data framesdf1 <- data.frame(x = c(1, 3), y = c(2, 4))df2 <- data.frame(x = c(5, 7), y = c(6, 8))# desired, combined data framedf3  <- data.frame(x = c(1, 3, 5, 7), y = c(2, 4, 6, 8),                   source = c("df1", "df1", "df2", "df2")# x y source# 1 2    df1# 3 4    df1# 5 6    df2# 7 8    df2我怎樣才能做到這一點(diǎn)？提前致謝！