在as.numeric()中避免使用NA

Question

如果我这样做,我会得到正确的结果:

a <- c("10","28","3")
which(as.numeric(a) == min(as.numeric(a)))
[1] 3

但是如果向量中有NA,则存在问题

a <- c("10","28","3","NA")
which(as.numeric(a) == min(as.numeric(a)))
integer(0)
Warning messages:
1: In which(as.numeric(a) == min(as.numeric(a))) :
  NAs introduced by coercion
2: In which(as.numeric(a) == min(as.numeric(a))) :
  NAs introduced by coercion

Answer 1

两件事情.

首先,字符串"NA"和缺失值的R数据表示之间存在差异NA.在示例中删除NA周围的引号,以查看:

a <- c("10","28","3",NA)

其次,当你使用min与实际缺失值(即不是字符串"NA"),你需要使用na.rm = TRUE:

which(as.numeric(a) == min(as.numeric(a),na.rm = TRUE))

Answer 2

您的主要问题是没有na.rm = TRUE在通话中指定min

numeric_a <- as.numeric(a)

which(numeric_a == min(numeric_a, na.rm = TRUE))
## [1] 3

或者您可以使用which.min不需要您指定应删除NA值的那些.这只会给你第一场比赛,而不是所有的比赛(感谢@Dason提醒我澄清一下)

which.min(numeric_a)