R: regexpr () how to use a vector in a template parameter

Question

I would like to know the provisions of the terms from a dictionary found in a set of short texts. The problem is the last lines of the following code, roughly based on From a list of lines identifying the names of people and which are not

library(tm)

pkd.names.quotes <- c(
  "Mr. Rick Deckard",
  "Do Androids Dream of Electric Sheep",
  "Roy Batty",
  "How much is an electric ostrich?",
  "My schedule for today lists a six-hour self-accusatory depression.",
  "Upon him the contempt of three planets descended.",
  "J.F. Sebastian",
  "Harry Bryant",
  "goat class",
  "Holden, Dave",
  "Leon Kowalski",
  "Dr. Eldon Tyrell"
) 


firstnames <- c("Sebastian", "Dave", "Roy",
                "Harry", "Dave", "Leon",
                "Tyrell")

dict  <- sort(unique(tolower(firstnames)))

corp <- VCorpus(VectorSource(pkd.names.quotes))
#strange but Corpus() gives wrong segment numbers for the matches.

tdm  <-
  TermDocumentMatrix(corp, control = list(tolower = TRUE, dictionary = dict))

inspect(corp)
inspect(tdm)

View(as.matrix(tdm))

data.frame(
  Name      = rownames(tdm)[tdm$i],
  Segment = colnames(tdm)[tdm$j],
  Content = pkd.names.quotes[tdm$j],
  Postion = regexpr(
    pattern = rownames(tdm)[tdm$i],
    text = tolower(pkd.names.quotes[tdm$j])
  )
)

Exit with a warning and only with the first line.

       Name Segment          Content Postion
1       roy       3        Roy Batty       1
2 sebastian       7   J.F. Sebastian      -1
3     harry       8     Harry Bryant      -1
4      dave      10     Holden, Dave      -1
5      leon      11    Leon Kowalski      -1
6    tyrell      12 Dr. Eldon Tyrell      -1

Warning message:
In regexpr(pattern = rownames(tdm)[tdm$i], text = tolower(pkd.names.quotes[tdm$j])) :
  argument 'pattern' has length > 1 and only the first element will be used

I know a solution with pattern = paste (vector, collapse = "|") , but my vector can be very long (all popular names).

Could there be a simple vector version of this command or a solution that for each line takes a new template parameter?

Answer 1

regexpr mapply:

mapply sapply. mapply FUN ... , , ..

data.frame(
  Name      = rownames(tdm)[tdm$i],
  Segment = colnames(tdm)[tdm$j],
  Content = pkd.names.quotes[tdm$j],
  Postion = mapply(regexpr, rownames(tdm)[tdm$i], tolower(pkd.names.quotes[tdm$j]), fixed=TRUE)
)

:

               Name Segment          Content Postion
roy             roy       3        Roy Batty       1
sebastian sebastian       7   J.F. Sebastian       6
harry         harry       8     Harry Bryant       1
dave           dave      10     Holden, Dave       9
leon           leon      11    Leon Kowalski       1
tyrell       tyrell      12 Dr. Eldon Tyrell      11

stringr str_locate:

:

str_locate - . , .

str_locate(tolower(pkd.names.quotes[tdm$j]), fixed(rownames(tdm)[tdm$i]))[,1]

, fixed() , ( ). fixed() fixed=TRUE.