Question

I am trying to extract integers of varying length from a data frame column ($description) that precedes a known string. For example, I wish to extract the integers that appear before the string “yard” in the following (each line represents a separate entry in the dataframe column):

(3:18) B.Green-Ellis left end to NE 28 for -1 yards (A.Ross).

(1:07) (No Huddle Shotgun) B.Green-Ellis right guard to NYG 27 for 4 yards (C.Blackburn).

(14:00) B.Green-Ellis right end pushed ob at NYG 33 for 17 yards (K.Phillips).

What makes it problematic is that the integer can vary in length (i.e. 4 or 17), but it can also be negative.

I really have tried everything I can think of, and have been searching all day for a related thread!

Answer 1

A very simple solution would be

s1 <- "(3:18) B.Green-Ellis left end to NE 28 for -1 yards (A.Ross)."
ss1 <- strsplit(s1, split = " ")[[1]]
as.numeric(ss1[grep("yards", ss1) -1])

now you just have to put this in a loop and apply to every row, i.e

s1 <- "(3:18) B.Green-Ellis left end to NE 28 for -1 yards (A.Ross)."
s2 <- "(1:07) (No Huddle Shotgun) B.Green-Ellis right guard to NYG 27 for 4 yards  (C.Blackburn)."
s3 <- "(14:00) B.Green-Ellis right end pushed ob at NYG 33 for 17 yards (K.Phillips)."

df <- rbind(s1,s2,s3)

splits <- strsplit(df[, 1], split = " ")
sapply(splits, function(z) z[grep("yards", z) - 1])

you can also do this in one step, as @joshua suggested!