create(mutate) column with a condition of another one - r

Question

I have this data
COL
AABC1
AAAABD2
AAAAAABF3
I would like to make a certain column like this:
COL NEW_COL
AABC1 T1
AAAABD2 T2
AAAAAABF3 T3
If COL contains 'BC', NEW_COL will be T1
contains 'BD', it will be T2
contains 'BF', it will be T3.
I would like to use mutate and grepl function but I have 80 conditions (like BC>T1) so that the code does not work in the R.
With the table like:
CLASS NEW_COL
BC T1
BD T2
BF T3
Could I use mutate(create) new column with above standard table ??

Answer 1

Here's your data:
DF <- data.frame(COL = c("AABC1",
"AAAABD2",
"AAAAABF3"),
stringsAsFactors = FALSE)
lookup_tbl <- data.frame(CLASS = c("BC", "BD", "BF"),
NEW_COL = c("T1", "T2", "T3"),
stringsAsFactors = FALSE)
Your problem is solved by a join, after some initial preparation.
To prepare DF, you need to add a column that extracts any instance of CLASS in the lookup table from COL in DF. Then you can join normally. In R:
library(dplyr)
DF %>%
mutate(CLASS = gsub(paste0("^.*(",
paste0(lookup_tbl[["CLASS"]], collapse = "|"),
").*$"),
"\\1",
lookup_tbl[["CLASS"]])) %>%
# or inner_join as required
left_join(lookup_tbl, by = "CLASS")
How the solution should behave COL matches zero or more than one instance in CLASS will need to be specified. The above handles both cases, but maybe not how you'd like.

Answer 2

You can create a lookup table with your 80 conditions and write a little function to match against it. Here's an example (normally, you'd read in lookup_table from file, I'm guessing):
library(tidyverse)
lookup_table <- data.frame(
row.names = c('BC', 'BD', 'BF'),
new_col = c('T1', 'T2', 'T3'),
stringsAsFactors = FALSE)
lookup <- function(x, table) {
for (class in rownames(table)) {
if (grepl(class, x)) {
return(table[class, 'new_col'])
}
}
}
data_frame(col = c('AABC1', 'AAAABD2', 'AAAAAABF3')) %>%
rowwise %>% mutate(new_col = lookup(col, lookup_table))
Note that this will take the first match it finds, so be sure your lookup table is ordered properly with respect to the priority you want to give the matching rules.