Question

我正在努力使用正则表达式，因此任何见解都会有所帮助。我有一个这样的列表：

[1] "collected 1 hr total. wind >15 mph."   "collected 4 hr total. 
wind ~15 mph."  
[3] "collected 10 hr total. gusts 5-10 mph." "collected 1 hr total. 
breeze at 1mph," 
[5] "collected 2 hrs."    [6]

我想要：

 [1] > 15 mph
 [2] ~15 mph
 [3] 5-10 mph
 [4] 1mph
 [5] 
 [6]

我想在每一行中拉出风速。您能建议正确的正则表达式吗？如你看到的， a）数字和“ mph”之间可以有可变数量的空格 b）mph之前的数字可以有不同的符号“>”，“ <”，“〜”，也可以是间隔“-”

提前谢谢！

Answer 1

假设每个字符串最多只有一个匹配项，那么我们可以尝试将sapply和sub一起使用：

input <- c("collected 1 hr total. wind >15 mph.",
           "collected 4 hr total. wind ~15 mph.",
           "collected 10 hr total. gusts 5-10 mph.",
           "collected 1 hr total. breeze at 1mph,",
           "collected 2 hrs.")

matches <- sapply(input, function(x) {
    ifelse(grepl("[>~0-9-]+\\s*mph", x),
           sub(".*?([>~0-9-]+\\s*mph).*", "\\1", x),
           "")})

names(matches) <- c(1:length(matches))
matches

         1          2          3          4          5 
 ">15 mph"  "~15 mph" "5-10 mph"     "1mph"         ""

Answer 2

带有str_extract

的一个选项

library(stringr)
trimws(str_extract(v1, "[>~]?[0-9- ]+mph"))
#[1] ">15 mph"   "~15 mph"   "5-10 mph" "1mph"     NA

数据

v1 <- c("collected 1 hr total. wind >15 mph.", 
   "collected 4 hr total. wind ~15 mph.", 
 "collected 10 hr total. gusts 5-10 mph.", 
 "collected 1 hr total. breeze at 1mph,", 
  "collected 2 hrs.")

在短语前拔出数字

2 个答案:

数据