R apply user define function on data frame columns

问题:

in R I have a function define to calculate intersection between 2 strings:

containedin <- function(t1,t2){
  return length(Reduce(intersect, strsplit(c(t1,t2), "\\s+"))) 
}

I want to apply this function on a data frame that contains 2 string columns: data.selected[c('keywords','title')]

keywords                                                                             title
1  Samsung UN48H6350 48" Samsung UN48H6350 48" Full 1080p Smart HDTV 120Hz with Wi-Fi +$50 Visa Gift Card
2  Samsung UN48H6350 48"     Samsung UN48H6350 48" Full HD Smart LED TV -Bundle- (See Below for Contents)
3  Samsung UN48H6350 48"      Samsung UN48H6350 48" Class Full HD Smart LED TV -BUNDLE- See below Details
4  Samsung UN48H6350 48"     Samsung UN48H6350 48" Full HD Smart LED TV With BD-H5100 Blu-ray Disc Player
5  Samsung UN48H6350 48"                 Samsung UN48H6350 48" Smart 1080p Clear Motion Rate 240 LED HDTV
6  Samsung UN48H6350 48"            Samsung UN48H6350 - 48-Inch Full HD 1080p Smart HDTV 120Hz with Wi-Fi
7  Samsung UN48H6350 48"               Samsung 6350 Series UN48H6350 48" 1080p HD LED LCD Internet TV NEW
8  Samsung UN48H6350 48"  Samsung Un48h6350af 75" 1080p Led-lcd Tv - 16:9 - Hdtv 1080p - (un75h6350afxza)
9  Samsung UN48H6350 48"                         Samsung UN48H6350 - 48" HD 1080p Smart HDTV 120Hz Bundle
10 Samsung UN48H6350 48"   Samsung UN48H6350 - 48-Inch Full HD 1080p Smart HDTV 120Hz with Wi-Fi, (R#416)

How do I use the apply function to be applied on these 2 columns, to return a new column with the result ?

回答1:

First of all, your return statement should really give you an error. You probably mean

containedin <- function(t1,t2){
  length(Reduce(intersect, strsplit(c(t1,t2), "\\s+"))) 
}

Anyway, you can use mapply to solve your problem.

mapply(containedin, 
       as.character(data.selected[, 'keywords']), 
       as.character(data.selected[, 'title']))

The as.character is only necessary if class(data.selected[, 'keywords']) is factor (instead of character)