数据集中的模式匹配

Question

been struggling with this for a while.

I have a dataset with two columns, a Description column and the other is the pattern column that I am trying to match against the description column.If the corresponding pattern exists in the Description column, it needs to be replaced by an asterisk

For instance, if the Description is ABCDEisthedescription and the Pattern is ABCDE, then the new description should *isthedescription

I tried the following data$NewDescription <- gsub(data$pattern,"\\\\*",Data$Description )

since there is more than one row in the dataset, it throws an error ( a warning rather) "argument 'pattern' has length > 1 and only the first element will be used"

Any help will be hugely appreciated.

Answer 1

You can use an mapply here to apply the function to each row.

#sample data
data<-data.frame(
    pattern=c("ABCDE","XYZ"), 
    Description=c("ABCDEisthedescription", "sillyXYZvalue")
)

Now use mapply

mapply(function(p,d) gsub(p, "\\*", d, fixed=T), data$pattern, data$Description)
# [1] "\\*isthedescription" "silly\\*value" 

Answer 2

Additionally,

Patterns <- paste0(
  sample(LETTERS[1:4],500,replace=TRUE),
  sample(LETTERS[1:4],500,replace=TRUE),
  sample(LETTERS[1:4],500,replace=TRUE),
  sample(LETTERS[1:4],500,replace=TRUE))
##
Desc <- paste0(Patterns,"isthedescription")
Ptrn <- sample(Patterns,500)
##
Data <- data.frame(
  Description=Desc,
  Pattern=Ptrn,
  stringsAsFactors=FALSE)
##
newDesc <- sapply(1:nrow(Data), function(X){
  if(substr(Data$Description[X],1,4)==Data$Pattern[X]){
    gsub(Data$Pattern[X],"*",Data$Description[X])
  } else {
    Data$Description[X]
  }
})

@MrFlick's approach seems more concise though.