[英]Removing strings from rows for specific words
My Data looks like:我的数据看起来像:
Weather
<chr>
1 Snow Low clouds
2 Snow Cloudy
3 Drizzle Fog
4 Thundershowers Partly cloudy
5 Thunderstorms More clouds than sun
6 Sprinkles Partly cloudy
7 Heavy rain Broken clouds
8 Light rain Partly cloudy
I am trying to use mutate
to remove some text.我正在尝试使用mutate
来删除一些文本。 For example I would like the above to look like:例如,我希望上面看起来像:
Weather
<chr>
1 Snow
2 Snow
3 Drizzle
4 Thundershowers
5 Thunderstorms More clouds than sun
6 Sprinkles Partly cloudy
7 Heavy rain
8 Light rain
So I would like to remove the text after some specific words.所以我想删除一些特定单词之后的文本。 If I have a vector of the following:如果我有以下向量:
c("Snow", "Drizzle", "Heavy rain", "Light rain")
Remove the text after these.删除这些后面的文字。 However I do not want to grep
words such as Cloudy
, Fog
since they occure as their own row in the data but something like Snow Light fog
can be cut down to Snow
.但是,我不想grep
诸如Cloudy
、 Fog
词,因为它们在数据中作为自己的行出现,但是诸如Snow Light fog
类的东西可以分解为Snow
。
Data:数据:
d <- structure(list(Weather = c("Snow Low clouds", "Snow Cloudy",
"Drizzle Fog", "Thundershowers Partly cloudy", "Thunderstorms More clouds than sun",
"Sprinkles Partly cloudy", "Heavy rain Broken clouds", "Light rain Partly cloudy",
"Rain showers Passing clouds", "Thundershowers Scattered clouds",
"Thundershowers Passing clouds", "Light snow Overcast", "Snow Light fog",
"Drizzle Broken clouds", "Light rain Fog", "Cloudy", "Thunderstorms Partly cloudy",
"Heavy rain More clouds than sun", "Partly cloudy", NA)), class = c("tbl_df",
"tbl", "data.frame"), row.names = c(NA, -20L))
A general approach you can take here is to build a regex alternation of all target terms.您可以在此处采用的一般方法是构建所有目标术语的正则表达式交替。 Then, match those terms followed by anything up until the end of the input, and replace with just the term.然后,匹配这些术语后跟任何内容直到输入结束,并仅替换为术语。
terms <- c("Snow", "Drizzle", "Heavy rain", "Light rain")
regex <- paste0("\\b(", paste(terms, collapse="|"), ")\\b")
sub(paste0(regex, "\\s.*"), "\\1", d$Weather)
[1] "Snow" "Snow"
[3] "Drizzle" "Thundershowers Partly cloudy"
[5] "Thunderstorms More clouds than sun" "Sprinkles Partly cloudy"
[7] "Heavy rain" "Light rain"
[9] "Rain showers Passing clouds" "Thundershowers Scattered clouds"
[11] "Thundershowers Passing clouds" "Light snow Overcast"
[13] "Snow" "Drizzle"
[15] "Light rain" "Cloudy"
[17] "Thunderstorms Partly cloudy" "Heavy rain"
[19] "Partly cloudy" NA
Note that my output does not line up exactly with your expected output, but then again you did not include all target words in the suggested vector.请注意,我的输出与您的预期输出不完全一致,但是您再次没有在建议的向量中包含所有目标词。
The regex I used was:我使用的正则表达式是:
\b(Snow|Drizzle|Heavy rain|Light rain)\b
The trick here is that the above alternation is also a capture group, letting us easily replace the match with just the term you want.这里的技巧是上述交替也是一个捕获组,让我们可以轻松地用您想要的术语替换匹配项。 You may add more terms to this to get the desired output.您可以为此添加更多术语以获得所需的输出。
v <- c("Snow", "Drizzle", "Heavy rain", "Light rain")
pat <- paste0(v,collapse = "|")
unlist(regmatches(d$Weather,gregexpr(pat,d$Weather)))
such that以至于
> unlist(regmatches(d$Weather,gregexpr(pat,d$Weather)))
[1] "Snow" "Snow" "Drizzle" "Heavy rain" "Light rain" "Snow"
[7] "Drizzle" "Light rain" "Heavy rain"
d
in a new column, then you can use the following code:如果要添加提取的值并将它们附加到新列中的d
,则可以使用以下代码:d <- within(d,X <- ifelse(grepl(pat,Weather),unlist(regmatches(Weather,gregexpr(pat,Weather))),NA))
such that以至于
> d
# A tibble: 20 x 2
Weather X
<chr> <chr>
1 Snow Low clouds Snow
2 Snow Cloudy Snow
3 Drizzle Fog Drizzle
4 Thundershowers Partly cloudy NA
5 Thunderstorms More clouds than sun NA
6 Sprinkles Partly cloudy NA
7 Heavy rain Broken clouds Drizzle
8 Light rain Partly cloudy Light rain
9 Rain showers Passing clouds NA
10 Thundershowers Scattered clouds NA
11 Thundershowers Passing clouds NA
12 Light snow Overcast NA
13 Snow Light fog Heavy rain
14 Drizzle Broken clouds Light rain
15 Light rain Fog Snow
16 Cloudy NA
17 Thunderstorms Partly cloudy NA
18 Heavy rain More clouds than sun Heavy rain
19 Partly cloudy NA
20 NA NA
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