Question

如果匹配正则表达式

，我想在数据框列中扩展某些字符串

输入：

FD_Object<-list(x="a stricture",x="an ulcer",x="inflammation",x="a nodule",x="a polyp")
FD_Location<-list(x="oesophagus at (cm)",x="GOJ",x="fundus",x="stomach body",x="stomach antrum",x="duodenal bulb",x="D1/D2 angle",x="second part of the duodenum",x="third part of the duodenum")
FD_LesionGen<-list(x="Flat",x="friable",x="nodular",x="malignant-looking")

FD1<-replicate(1000,paste("There is",sample(FD_Object,1,replace=F),"in the",sample(FD_Location,1,replace=F),".It is",sample(3:10,1),"mm in length and ",sample(FD_LesionGen,1,replace=F)))

FD1<-data.frame(FD1)

到目前为止我的尝试：

   if (str_detect(FD1[,1],"polyp")){
  paste("Hi",FD1[1,])
}

但是我收到了错误：

Error in if (str_match(FD1[, 1], "polyp")) { : 
  argument is not interpretable as logical
In addition: Warning message:
In if (str_match(FD1[, 1], "polyp")) { :
  the condition has length > 1 and only the first element will be used

如何使匹配合乎逻辑？

Answer 1

您可以使用grepl：

a <- letters[1:3]
bool <- grepl("b", a)
a[bool] <- paste("pre", a[bool])

Answer 2

另一种选择可能是

library(dplyr)
library(stringr)

FD1 %>% 
  mutate(FD1 = ifelse(str_detect(FD1, "polyp"), paste("Hi", FD1), as.character(FD1)))

Answer 3

尝试str_detect()而不是str_match()。

Answer 4

您的问题是，您要给grepl或str_detect一个字符串向量进行检查，以便您的输出是逻辑向量。您可以使用apply将条件函数单独应用于每个元素：

out <- apply(FD1, 1, function(x) {
    if (stringr::str_detect(x, "polyp")) {
        return(paste("Hi", x))
    } else {
        return(x)
    }
})

r中的条件字符串扩展

4 个答案: