how to match strings of vectors with dataframe column in R

Question

I have following dataframe in r

Id    titles
1     emami paper mills slips 10% on dismal q4 numbers
2     jsw steel q4fy17 standalone net profit rises 173.33%
3     fmcg major hul q4fy17 standalone net profit rises 6.2
4     chennai petroleum, allsec tech slip 6-7% on poor q4

And, I have names in vectors

names <- c("emami ltd","jsw steel ltd","abc","hul india ltd","tcs","chennai petroleum corp ltd")

I want to match the dataframe column titles with strings of vectors and print corresponding string in a new column. My desired dataframe is

 Id    titles                                                    names
1     emami paper mills slips 10% on dismal q4 numbers           emami ltd
2     jsw steel q4fy17 standalone net profit rises 173.33%       jsw steel ltd
3     fmcg major hul q4fy17 standalone net profit rises 6.2      hul india ltd
4     chennai petroleum, allsec tech slip 6-7% on poor q4        chennai petroleum corp ltd

I am doing it with following code,but it does not give me what I want.

df[grepl(paste(names, collapse="|"), df$titles),]

How to do it in R?

Answer 1

If I understood you correctly then , you can use BaseR's gregexpr along with regematches and gsub to complete your task.

Data : EDIT After OP has changed the question

options(stringsAsFactors = F)
df <- data.frame(titles = c("emami paper mills slips 10% on dismal q4 numbers",
                            "jsw steel q4fy17 standalone net profit rises 173.33%",
                            "fmcg major hul q4fy17 standalone net profit rises 6.2",
                            "chennai petroleum, allsec tech slip 6-7% on poor q4"),stringsAsFactors = F)

names <- c("emami ltd","jsw steel ltd","abc","hul india ltd","tcs","chennai petroleum corp ltd")

Regex :

library(dplyr)
library(stringr)

newnames <- gsub("^(\\w+).*","\\1",names)
regmat <- regmatches(df$titles,gregexpr(paste0(newnames,collapse="|"),df$titles))
regmat[lapply(regmat,length) == 0] <- NA
df <- data.frame(cbind(df,newnames =do.call("rbind",regmat)),stringsAsFactors = F)
df1 <- data.frame(names=names,newnames=newnames,stringsAsFactors = F)
left_join(df,df1,by="newnames")

You can also use stringr library like below:

library(stringr)
newnames <- str_replace(names,"^(\\w+).*","\\1")
df$newnames <- str_extract(df$titles,paste0(newnames,collapse="|"))
df1 <- data.frame(names=names,newnames=newnames,stringsAsFactors = F)
left_join(df,df1,by="newnames")

output :

    > left_join(df,df1,by="newnames")
                                                 titles newnames                      names
1      emami paper mills slips 10% on dismal q4 numbers    emami                  emami ltd
2  jsw steel q4fy17 standalone net profit rises 173.33%      jsw              jsw steel ltd
3 fmcg major hul q4fy17 standalone net profit rises 6.2      hul              hul india ltd
4   chennai petroleum, allsec tech slip 6-7% on poor q4  chennai chennai petroleum corp ltd

Answer 2

从您的名字中删除有限公司：

names <- gsub(" ltd","",names)

Answer 3

It's also possible to use sqldf for this type of "fuzzy" merge.

Construct lookup:

names <- data.frame(name = c("emami ltd","jsw steel ltd","abc","hul india ltd","tcs"))
names$lookup <- gsub("(\\w+).*", "\\1", names$name)

Perform merge:

library(sqldf)
res <- sqldf("SELECT l.*, r.name
       FROM df as l
       LEFT JOIN names as r
       ON l.titles LIKE '%'||r.lookup||'%'")

A few notes: I extract the first word from the lookup since you said you want "hul" only, and not "hul india" . Also in sql the || means concatenate and % means wildcard (which will match anything), so this will match if any of the lookups appear anywhere in the text no matter what is before or after it.

---

Another option using Reduce and then merging would be:

df$lookup <- Reduce( function(x, y) {x[grepl(y,x)] <- y; x}, c(list(df$titles), names$lookup))
merge(df, names)

Answer 4

To add to the previous answer I have made a function including some of the previous comments :

df <-  data.frame(title=c("emami paper mills slips 10% on dismal q4 numbers",
                            "jsw steel q4fy17 standalone net profit rises 173.33%",
                            "fmcg major hul q4fy17 standalone net profit rises 6.2"))


names <- c("emami ltd","jsw steel ltd","abc","hul india ltd","tcs")

find_string <- function(data,names){

    ### Clean the names 
    newnames <- gsub("^(\\w+).*","\\1",names)

    ### Loop over the names to find which sentence contain it
    for(i in 1:length(newnames)){

        if(length(grep(newnames[i],df$title)) != 0){
            df$names[grep(newnames[i],df$title)] <- newnames[i]

        }else{
            print(paste(names[i],"not found in the data!"))
        }
    }
    return(df)
}

### Run the function

find_string(df,names)

Hope this helps !