正则表达式grep-parsing来自2个变量

The purpose is to collapse/re-assign levels as part of cleaning a dataset.

目的是在清理数据集时折叠/重新分配级别。

Here is the example:

这是一个例子:

df <- data.frame(V1 <- c("cat","lion","cat","beast","cat"),
             V2 <- c("nice and grumpy","angry","old,but also nice","empty","has friends"),
             stringsAsFactors = F); colnames(df) <- c("V1","V2")
>df
     V1          V2
1   cat   nice and grumpy
2  lion             angry
3   cat   old,but also nice
4 beast             empty
5   cat       has friends

The level of interest is cat; these are the entries:

感兴趣的程度是猫;这些是条目:

parse1 <- V1[grepl("cat",V1)]
#[1] "cat" "cat" "cat"

From there, the idea is to search for an attribute in V2, nice, upon which the level cat will be renamed as nice cat. This search locates 2 entries of interest in V2:

从那里,我们的想法是在V2中搜索一个属性,很好,等级cat将被重命名为好猫。此搜索在V2中找到2个感兴趣的条目:

 df.sub <- subset(df,V1=="cat",select=V1:V2)
 parse2 <- df.sub$V2[grep("([Nn]ice)",df.sub$V2)]
#[1] "nice and grumpy"   "old,but also nice"

The ideal final result would have df transformed to:

理想的最终结果将df转换为:

     V1                V2
1   nice cat   nice and grumpy
2   lion           king
3   nice cat   old,but also nice
4   beast           empty
5   cat        has friends

Any thoughts how to achieve this? Many thanks.

有什么想法如何实现这一点?非常感谢。

2 个解决方案

#1

An ifelse seems to be enough for this:

ifelse似乎足够了:

df$V1 <- ifelse(grepl("([Nn]ice)", df$V2), 
                sub('cat', 'nice cat', df$V1), 
                df$V1 )

Output:

> df
        V1                V2
1 nice cat   nice and grumpy
2     lion             angry
3 nice cat old,but also nice
4    beast             empty
5      cat       has friends

#2

You could use data.table

您可以使用data.table

df <- data.frame(V1 <- c("cat","lion","cat","beast","cat"),
         V2 <- c("nice and grumpy","angry","old,but also nice","empty","has friends"),
         stringsAsFactors = F); colnames(df) <- c("V1","V2")

library(data.table)
DT <- data.table(df)
# All the nice animals
DT[grepl ("([Nn]ice)",V2), V3:= paste0("nice ",V1)]
# All the nice cats
DT[grepl ("([Nn]ice)",V2) & V1=="cat", V4:= paste0("nice ",V1)]

#1