Question

Basically I’m looking to write a function that will take a vector of strings and a search term as input, and output a boolean vector. After this, I’d also like to take a list of strings and run it through this same function to output multiple results vectors, one for each string.

So the initial data looks like:

> searchVector <- cbind(c("aaa1","aaa2","","bbb1,aaa1,ccc1", "ddd1,ccc1,aaa1"))
> searchVector
     [,1]         
[1,] "aaa1"        
[2,] "aaa2"        
[3,] ""           
[4,] "bbb1,aaa1,ccc1"
[5,] "ddd1,ccc1,aaa1"

and this is what we’d hope to see:

>findTrigger(c("aaa","bbb"),searchVector)
         [aaa]  [bbb]
    [1,] 1     0   
    [2,] 1     0   
    [3,] 0     0      
    [4,] 1     1
    [5,] 1     0

I’ve made the following attempt:

searchfunction <- function (searchTerms, searchVector) {
  output = matrix( nrow = length(searchVector), 
             ncol = length(searchTerms), 
             dimnames = searchTerms)

  for (j in seq(1,length(searchTerms)))
  {
    for (i in seq(1,length(searchVector)))
    { 
      output[i,j]=is.numeric(pmatch(searchTerms[j], searchVector[i]))
    }
  }
  return(as.numeric(output))
}

But I just get a matrix of all 1’s. I’m fairly new to R and I’ve looked around online, but haven’t had any luck. Any help would be greatly appreciated, Thanks!

Answer 1

mapply and grep or grepl (thanks joran) are your friend:

searchTerms <- c("aaa", "bbb")
searchVector <- cbind(c("aaa1","aaa2","","bbb1,aaa1,ccc1", "ddd1,ccc1,aaa1"))
M <- mapply(grepl, searchTerms, MoreArgs=list(x=searchVector)) 
M
       aaa   bbb
[1,]  TRUE FALSE
[2,]  TRUE FALSE    
[3,] FALSE FALSE
[4,]  TRUE  TRUE
[5,]  TRUE FALSE

If you want it as 1,0: apply(M,2,as.numeric)