使用字符串列表在字符串中搜索并返回匹配答案

【问题标题】：Search in character string with list of strings and return match使用字符串列表在字符串中搜索并返回匹配
【发布时间】：2018-10-15 22:43:03
【问题描述】：

在 R 中，我想按照标题所说的那样做。在字符列中搜索并返回匹配的单词

As.data.frame(
    c("yellow carrot","big car","green tomato","orange car","fertile goat","red snapper")
    )

还有

c("yellow","red","orange","green","blue")

我想回来

As.data.frame(
    cbind(
        c("yellow carrot","big car","green tomato","orange car","fertile goat","red snapper"),
        c("yellow","NA","green","orange","NA","red")
        )

【问题讨论】：

奇怪的大写是怎么回事？ R 区分大小写，因此不是有效的 R 代码。
试试stringr::str_extract(df1[[1]], paste(vec1, collapse="|"))
对不起 - 写在手机上

标签： r string dataframe character

【解决方案1】：

我们可以使用str_extract来获取匹配的子串

library(stringr)
df1$new <- str_extract(df1[[1]], paste(vec1, collapse="|")) 
df1$new
#[1] "yellow" NA       "green"  "orange" NA       "red"

数据

vec1 <- c("yellow","red","orange","green","blue")
df1 <- data.frame(col1 = c("yellow carrot","big car",
  "green tomato","orange car","fertile goat","red snapper"))

【讨论】：

【解决方案2】：

使用dplyr 和ifelse 语句，并且在颜色不在字符串开头时有效。

data.frame(
    vary_1 = c(
        "yellow carrot",
        "big car",
        "green tomato",
        "orange car",
        "fertile goat",
        "red snapper"
    )
) %>%
    mutate(new = ifelse(grepl('yellow', .$vary_1),'yellow',
        ifelse(grepl('green', .$vary_1),'green',
            ifelse(grepl('red', .$vary_1),'red',
                   ifelse(grepl('orange',.$vary_1),'orange',
            NA
        )))))
    )

         vary_1    new
1 yellow carrot yellow
2       big car   <NA>
3  green tomato  green
4    orange car orange
5  fertile goat   <NA>
6   red snapper    red

【讨论】：

【解决方案3】：

使用grepl 的基本 R 解决方案：

# Sample data
df <- data.frame(V1 = c("yellow carrot","big car","green tomato","orange car","fertile goat","red snapper"))
s <- c("yellow","red","orange","green","blue")

df$new <- apply(df, 1, function(x)
    ifelse(length(ret <- s[sapply(s, function(y) grepl(y, x))]) > 0, ret, NA))
df;
#             V1    new
#1 yellow carrot yellow
#2       big car   <NA>
#3  green tomato  green
#4    orange car orange
#5  fertile goat   <NA>
#6   red snapper    red

【讨论】：