flag specific pattern using string r - r

Question

I am working with a data set where I need to flag all specific codes that start with "C13.xxx." There are other tree codes in the column and all tree codes are separated as follows: "C13.xxx|B12.xxx" - and all tree codes have a period in them. But the data set has other variables that are causing my string r function to flag characters that are not tree codes. Example:
library(tidyverse)
# test data
test <- tribble(
~id, ~treecode, ~contains_c13_xxx,
#--|--|----
1, "B12.123|C13.234.432|A11.123", "yes",
2, "C12.123|C13039|", "no"
)
# what I tried
test %>% mutate(contains_C13_error = ifelse(str_detect(treecode, "C13."), 1, 0))
# code above is flagging both id's as containing C13.xxx
in id 2, there is a variable that begins with C13, but it is not a tree codes (all tree codes have a period). The contains_c13_xxx variable is what I would like the code to produce. In the string detect function, I specified the period, so I'm not sure what is going wrong here.

Answer 1

The tricky part is there are multiple tree codes in the same column with a separator which makes it difficult to flag. We can bring each treecode into separate rows and then check for the code that we need. Using separate_rows from tidyr.
library(dplyr)
test %>%
tidyr::separate_rows(treecode, sep = "\\|") %>%
group_by(id) %>%
summarise(contains_C13_error = any(startsWith(treecode, "C13.")),
treecode = paste(treecode, collapse = "|"))
# A tibble: 2 x 3
# id contains_C13_error treecode
# <dbl> <lgl> <chr>
#1 1 TRUE B12.123|C13.234.432|A11.123
#2 2 FALSE C12.123|C13039|
This is assuming that there could be codes of the pattern "C13" without a dot. If the treecode would always have "C13" followed by a dot then simply escaping the dot in your regex would work.

Answer 2

Base R solution:
# Split on the | delim:
split_treecode <- strsplit(df$treecode, "[|]")
# Roll out the ids the number of times of each relevant treecode:
rolled_out_df <- data.frame(id = rep(df$id, sapply(split_treecode, length)), tc = unlist(split_treecode))
# Test whether or not string contains "C13"
rolled_out_df$contains_c13_xxx <- grepl("C13.", rolled_out_df$tc, fixed = T)
# Does the id have an element containing "C13" ?
rolled_out_df$contains_c13_xxx <- ifelse(ave(rolled_out_df$contains_c13_xxx,
rolled_out_df$id,
FUN = function(x){as.logical(sum(x))}), "yes", "no")
# Build back orignal df:
df <- merge(df[,c("id", "treecode")], unique(rolled_out_df[,c("id", "contains_c13_xxx")]), by = "id")
Data:
df <-
structure(
list(
id = c(1, 2),
treecode = c("B12.123|C13.234.432|A11.123",
"C12.123|C13039|"),
contains_c13_xxx = c("yes", "no")
),
row.names = c(NA,-2L),
class = "data.frame"
)