获取R中两个单词之间的距离

Question

Say I have a line in a file:

string <- "thanks so much for your help all along. i'll let you know when...."

I want to return a value indicating if the word know is within 6 words of help .

Answer 1

This is essentially a very crude implementation of Crayon's answer as a basic function:

withinRange <- function(string, term1, term2, threshold = 6) {
  x <- strsplit(string, " ")[[1]]
  abs(grep(term1, x) - grep(term2, x)) <= threshold
}

withinRange(string, "help", "know")
# [1] TRUE

withinRange(string, "thanks", "know")
# [1] FALSE

---

I would suggest getting a basic idea of the text tools available to you, and using them to write such a function. Note Tyler's comment: As implemented, this can match multiple terms ("you" would match "you" and "your") leading to funny results. You'll need to determine how you want to deal with these cases to have a more useful function.

Answer 2

you won't be able to get this from regex alone. I suggest splitting using space as delimiter, then loop or use a built-in function to do array search of your two terms and subtract the difference of the indexes (array positions).

edit: Okay I thought about it a second and perhaps this will work for you as a regex pattern:

\\bhelp(\\s+[^\\s]+){1,5}+\\s+know\\b

This takes the same "space is the delimiter" concept. First matches for help then greedily up to 5 " word" then looks for " know" (since "know" would be the 6th).

Answer 3

Split your string:

> words <- strsplit(string, '\\s')[[1]]

Build a indices vector:

> indices <- 1:length(words)

Name indices:

> names(indices) <- words

Compute distance between words:

> abs(indices["help"] - indices["know"]) < 6
FALSE

EDIT In a function

 distance <- function(string, term1, term2) {
    words <- strsplit(string, "\\s")[[1]]
    indices <- 1:length(words)
    names(indices) <- words
    abs(indices[term1] - indices[term2])
 }

 distance(string, "help", "know") < 6

EDIT Plus

There is a great advantage in indexing words, once its done you can work on a lot of statistics on a text.