Running R 3.1.1 on windows 7
I want to identify as a case any record in a dataframe that contains any
of several keywords in any of several variables.
Example:
# create a dataframe with 4 variables and 10 records
v2 <- c("white bird", "blue bird", "green turtle", "quick brown fox",
"big black dog", "waffle the hamster", "benny likes food a lot", "hello
world", "yellow giraffe with a long neck", "black bear")
v3 <- c("harry potter", "hermione grainger", "ronald weasley", "ginny
weasley", "dudley dursley", "red sparks", "blue sparks", "white dress
robes", "gandalf the white", "gandalf the grey")
zz <- data.frame(v1=rnorm(10), v2=v2, v3=v3, v4=rpois(10, lambda=2),
stringsAsFactors=FALSE)
str(zz)
zz
# here are the keywords
alarm.words <- c("red", "green", "turtle", "gandalf")
# For each row/record, I want to test whether the string in v2 or the
string in v3 contains any of the strings in alarm.words. And then if so,
set zz$v5=TRUE for that record.
# I'm thinking the str_detect function in the stringr package ought to
be able to help, perhaps with some use of apply over the rows, but I
obviously misunderstand something about how str_detect works
library(stringr)
str_detect(zz[,2:3], alarm.words) # error: the target of the search
# must be a vector, not multiple
# columns
str_detect(zz[1:4,2:3], alarm.words) # same error
str_detect(zz[,2], alarm.words) # error, length of alarm.words
# is less than the number of
# rows I am using for the
# comparison
str_detect(zz[1:4,2], alarm.words) # works as hoped when
length(alarm.words) # confining nrows
# to the length of alarm.words
str_detect(zz, alarm.words) # obviously not right
# maybe I need apply() ?
my.f <- function(x){str_detect(x, alarm.words)}
apply(zz[,2], 1, my.f) # again, a mismatch in lengths
# between alarm.words and that
# in which I am searching for
# matching strings
apply(zz, 2, my.f) # now I'm getting somewhere
apply(zz[1:4,], 2, my.f) # but still only works with 4
# rows of the dataframe
# perhaps %in% could do the job?
Appreciate any advice.
--Chris Ryan
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