相关疑难解决方法(0)

难道ifelse真的同时计算yes和no载体-如,每个向量的全部？或者它只是从每个向量计算一些值？

还有,ifelse真的那么慢吗？

考虑以下数据框：

(tmp_df <-
structure(list(class = c(0L, 0L, 1L, 1L, 2L, 2L), logi = c(TRUE, 
FALSE, TRUE, FALSE, TRUE, FALSE), val = c(1, 1, 1, 1, 1, 1), 
    taken = c(1.00684931506849, 0.993197278911565, 1.025, 0.975609756097561, 
    1.00826446280992, 0.991803278688525)), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -6L), .Names = c("class", 
"logi", "val", "taken")))

这会创建：

Source: local data frame [6 x 4]

  class  logi   val     taken
  <int> <lgl> <dbl>     <dbl>
1     0  TRUE     1 1.0068493
2     0 FALSE     1 0.9931973
3     1  TRUE     1 …