如何从R数据框中的字符列中提取第一位数字？
如果我们在数据框中有一个字符列，其中包含字符串以及数字值，并且数字值的第一位具有可以帮助进行数据分析的含义，那么我们可以提取这些第一位。为此，我们可以使用stringi包中的stri_extract_first函数。
例1
考虑以下数据帧-
> x1<-1:20
> y1<-sample(c("HT23L","HT14L","HT32L"),20,replace=TRUE)
> df1<-data.frame(x1,y1)
> df1输出结果x1 y1 1 1 HT14L 2 2 HT14L 3 3 HT23L 4 4 HT14L 5 5 HT32L 6 6 HT32L 7 7 HT14L 8 8 HT32L 9 9 HT32L 10 10 HT32L 11 11 HT23L 12 12 HT32L 13 13 HT14L 14 14 HT23L 15 15 HT14L 16 16 HT23L 17 17 HT23L 18 18 HT23L 19 19 HT23L 20 20 HT23L
加载stringi包并提取y1列中的第一位-
> library(stringi) > stri_extract_first(df1$y1,regex="\\d")输出结果
[1] "1" "1" "2" "1" "3" "3" "1" "3" "3" "3" "2" "3" "1" "2" "1" "2" "2" "2" "2" [20] "2"
例2
> x2<-sample(c("India1RT1","UK5RT1","Egypt2PT4"),20,replace=TRUE)
> y2<-rpois(20,5)
> df2<-data.frame(x2,y2)
> df2输出结果x2 y2 1 India1RT1 2 2 India1RT1 8 3 India1RT1 7 4 India1RT1 6 5 UK5RT1 6 6 India1RT1 5 7 UK5RT1 6 8 India1RT1 6 9 India1RT1 7 10 UK5RT1 10 11 Egypt2PT4 8 12 Egypt2PT4 5 13 Egypt2PT4 7 14 India1RT1 2 15 UK5RT1 3 16 Egypt2PT4 5 17 UK5RT1 3 18 Egypt2PT4 6 19 Egypt2PT4 3 20 UK5RT1 5
提取列x2中的第一位数字-
> stri_extract_first(df2$x2,regex="\\d")输出结果
[1] "1" "1" "1" "1" "5" "1" "5" "1" "1" "5" "2" "2" "2" "1" "5" "2" "5" "2" "2" [20] "5"
范例3
> x3<-sample(c("abc123","dfe456"),20,replace=TRUE)
> y3<-rnorm(20)
> df3<-data.frame(x3,y3)
> df3输出结果x3 y3 1 abc123 0.1027005 2 dfe456 0.2297002 3 dfe456 -0.1441151 4 dfe456 1.0510760 5 abc123 0.8182656 6 dfe456 -0.5018968 7 dfe456 0.2957634 8 abc123 -0.4240910 9 dfe456 -1.0700713 10 dfe456 -0.3374661 11 dfe456 -0.4654241 12 dfe456 -0.4542710 13 abc123 0.6969808 14 dfe456 -0.6514574 15 abc123 0.2258769 16 dfe456 -0.5348958 17 abc123 0.6629195 18 dfe456 1.0998636 19 dfe456 -1.3147809 20 dfe456 -2.3015384
提取列x3中的第一位数字-
> stri_extract_first(df3$x3,regex="\\d")输出结果
[1] "1" "4" "4" "4" "1" "4" "4" "1" "4" "4" "4" "4" "1" "4" "1" "4" "1" "4" "4" [20] "4"