r：遍历几列的所有元素以检测短语

Question

i am trying to loop through several columns in a dataframe which contain text files.

i want to check every entry of columns 7 through 16 to see if any of the text files contain a certain phrase.

each time the phrase is detected, i want to increase the count of times it appeared by 1.

this seems pretty straightforward. i think i should iterate through the columns and by the rows, but i just can't seem to figure out exactly how to do this.

any suggestions? thank you in advance for any insight.

fc_count <- 0

for (col in profiles[7:16]){
  for (row in 1:nrow(profiles)){

    if(isTRUE(grepl("my name is jeff", row)) == TRUE){

      fc_count = fc_count + 1

    }

  }

}

fc_count

Answer 1

We can use lapply to loop over the columns 7 to 16, apply grepl , with the pattern to get a list of logical vectors, Reduce , it to a single integer vector by adding ( + ) and then get the total value by sum

sum(Reduce(`+`, lapply(profiles[7:16], grepl, pattern = "my name is jeff")))

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As grepl is vectorized for vector , if we convert the 'data.frame' to a matrix ( a matrix is a vector with dim attributes), it is more compact

sum(grepl("my name is jeff", as.matrix(profiles[7:16])))

---

Also, with for loops, we don't need the nested loops as grepl is vectorized

fc_count <- 0
for(prf in profiles[7:16]){
    fc_count <- fc_count + sum(grepl("my name is jeff", prf))
 }