Unlist data frame column and pasting them together - r

Question

I have a dataframe as defined below:
df <- structure(list(ID = 1:19, MEDICATION = c("0", "NOVOMIX 26 BF, 20 D",
"NOVOMIX 14 D", "NOVOMIX 34 BF 22 D", "MIXTARD 52 BF 20 D", "MIXTARD 40 BF 24 D",
"MIXTARD 10 BF 8 D", "MIXTARD 42 BF 24 D", "MIXTARD 20 BF 18 D",
"MIXTARD 82 BF 46 D", "MIXTARD 14 BF 10 D", "NOVOMIX 15 BF 15 D",
"MIXTARD", NA, "MIXTARD 10 BF 4 D", "NOVOMIX", "MIXTARD --> NOVOMIX",
"NOT GIVEN ANY DIABETES MEDICATION INPATIENT PATIENT NORMALLY ON METFORMIN",
"GIVEN ASPART")), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, -19L), .Names = c("ID", "MEDICATION"))
I would like to extract all the medications (i.e. NOVOMIX, MIXTARD, METFORMIN, ASPART from the MEDICATION variable in the dataframe and paste them together. I wrote my code as follows:
library(tidyverse)
library(rebus)
df %>%
mutate(MEDICATION2 = str_extract_all(MEDICATION, pattern =
or1(c("NOVOMIX", "MIXTARD", "METFORMIN", "ASPART")))) %>%
unnest(MEDICATION2) %>%
group_by(ID) %>%
mutate(MEDICATION2 = str_c(unlist(MEDICATION2), collapse = " - ")) %>%
slice(1)
My expected output is:
df_out <- structure(list(ID = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19), MEDICATION = c("0", "NOVOMIX 26 BF, 20 D",
"NOVOMIX 14 D", "NOVOMIX 34 BF 22 D", "MIXTARD 52 BF 20 D", "MIXTARD 40 BF 24 D",
"MIXTARD 10 BF 8 D", "MIXTARD 42 BF 24 D", "MIXTARD 20 BF 18 D",
"MIXTARD 82 BF 46 D", "MIXTARD 14 BF 10 D", "NOVOMIX 15 BF 15 D",
"MIXTARD", NA, "MIXTARD 10 BF 4 D", "NOVOMIX", "MIXTARD --> NOVOMIX",
"NOT GIVEN ANY DIABETES MEDICATION INPATIENT PATIENT NORMALLY ON METFORMIN",
"GIVEN ASPART"), MEDICATION2 = c(NA, "NOVOMIX", "NOVOMIX", "NOVOMIX",
"MIXTARD", "MIXTARD", "MIXTARD", "MIXTARD", "MIXTARD", "MIXTARD",
"MIXTARD", "NOVOMIX", "MIXTARD", NA, "MIXTARD", "NOVOMIX", "MIXTARD - NOVOMIX",
"METFORMIN", "ASPART")), .Names = c("ID", "MEDICATION", "MEDICATION2"
), row.names = c(NA, -19L), class = "data.frame")
The problem is the code removed the row with MEDICATION == 0 and I think my code is too long for a simple extraction of strings. I would like to ask for help if you know how this code can be shorten (if possible).

Answer 1

We can use stri_extract_all_regex from the stringi package to extract all the words which matches the pattern.
library(stringi)
med_pattern <- c("NOVOMIX|MIXTARD|METFORMIN|ASPART")
df$MEDICATION2 <- stri_extract_all_regex(df$MEDICATION, pattern = med_pattern)
As mentioned by #mt1022, the new column is a list. We may paste them together with
df$MEDICATION2<-paste(stri_extract_all_regex(df$MEDICATION,pattern = med_pattern))
However, it will not give some unwanted characters for lists with more than 1 element. This should give you the expected output.
chars <- stri_extract_all_regex(df$MEDICATION, pattern = med_pattern)
df$MEDICATION2 <- sapply(chars, paste, collapse = "-")
df$MEDICATION2
#[1] "NA" "NOVOMIX" "NOVOMIX" "NOVOMIX"
#[5] "MIXTARD" "MIXTARD" "MIXTARD" "MIXTARD"
#[9] "MIXTARD" "MIXTARD" "MIXTARD" "NOVOMIX"
#[13] "MIXTARD" "NA" "MIXTARD" "NOVOMIX"
#[17] "MIXTARD-NOVOMIX" "METFORMIN" "ASPART"
You can also do this in single line :
df$MEDICATION2 <- sapply(stri_extract_all_regex(df$MEDICATION,
pattern = med_pattern), paste, collapse = "-")