Multiple Pattern matching in R over multiple files , multiple columns & rows - r

Question

I've a list of CSV files i need to read from , in which multiple files with columns such as Title, description .... . From these columns over multiple files , a retrieval operation has to be written and matched against another CSV generated from popular keywords(~10k) generated from a tool similar to WordStream SEO.
What i was able to do
#Not sure if this is correct approach
Source1<- read.csv(path to csv file)
Keywords_tomatch<- read.csv(path to csv file)
#cant really take both the columns into single vector and iterate over them
subColdesc <- Source1[,c(3)]
subcolTitle <-Source1[,c(2)]
keywordget<- subset(Keywords_tomatch,grepl("*",Keywords_tomatch$col1))
#Two individual vectors since i'm not sure whether sapply() can be applied over multiple lists Definition: sapply(list,function)
descBoolean <- sapply(keywordget,
function(y)
sapply(subColdesc ,
function(x)
any(grepl(y,x)))
)
TitleBoolean = sapply(keywordget,
function(y)
sapply(subcolTitle ,
function(x)
any(grepl(y,x)))
)
#matches just the first element in the column of keywordget against (~4k) elements in description,title column. i.e returns a warning/error
In grepl(y, x) :
argument 'pattern' has length > 1 and only the first element will be used
I've tried at Akrun's version of grep and it hadn't worked for me
Question :
How to match all the elements in the keywordget vector and retrieve what columns matched on each row of Description,Title and what rows of Description and Title have matched.
In short how to retrieve all the game related products in the Source1 using Keywords_tomatch?
As a sample i'm posting the two files i've gathered. Source1 only contains few rows of 4k rows
Source1 =1.csv,
Keywords_tomatch = Gaming.csv

Answer 1

First, let me point out some possible ways why your code is not working (and correct me if I am wrong):
Your files are read with stringAsFactors = TRUE, and grepl does recognize factor variables for the pattern = argument. But since you did not get an error about grepl not recognizing factors, I assume you converted them to characters before matching.
You need the fixed = TRUE argument for grepl or else it will treat the elements of keys as regular expressions.
Your keywordget is a dataframe, and R treats dataframes as lists when being called as one. So since the first argument of sapply takes a list, it treats keywordget as a list with 1 element. So when this element (which is essentially the entire vector of keywordget) is supplied to the pattern argument of the grepl function, you get the error:
In grepl(y, x) : argument 'pattern' has length > 1 and only the first element will be used
For example, this should work:
sapply(keywordget$GAMING, function(y) {
sapply(source1$title, function(x) {
any(grepl(y,x, fixed = TRUE))
})
})
Below is my solution:
# Read files
source1 = read.csv("source1.csv", stringsAsFactors = FALSE)
keys = read.csv("gaming.csv", stringsAsFactors = FALSE)
# Finds the index of elements in source1 that matches
# with any of the keys
matchIndex = lapply(source1, function(x){
which(Reduce(`|`, lapply(keys$GAMING, grepl, x, fixed = TRUE)))
})
> matchIndex
$title
integer(0)
$description
[1] 189 293 382 402 456
title has zero matches and description has 5
# Returns the descriptions that match
source1$description[matchIndex$description]
# Returns the title corresponding to the descriptions that match
source1$title[matchIndex$description]
> source1$title[matchIndex$description]
[1] "tomb raider: legend"
[2] "namco museum 50th anniversary collection"
[3] "restricted area"
[4] "south park chef's luv shack"
[5] "brainfood games cranium collection 2006"