Creating one variable from a list of variables in R?

Using base R, we can use sapply and use grepl to find pattern in every column and assign 1 to rows where there is more than 0 matches.

df$indicator <- as.integer(rowSums(sapply(df, grepl, pattern = code_regex)) > 0)

df
#  c1 c2 c3 indicator
#1 T1 R4 C5         1
#2 X1 C6 C2         0
#3 T6 C7 X4         0
#4 R5 X3 T2         1

If there are few other columns and we are interested to apply it only for columns which start with "c" we can use grep to filter them.

cols <- grep("^c", names(df))
as.integer(rowSums(sapply(df[cols], grepl, pattern = code_regex)) > 0)

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Using dplyr we can do

library(dplyr)

df$indicator <- as.integer(df %>%
              mutate_at(vars(c1:c3), ~grepl(code_regex, .)) %>%
              rowSums() > 0)

We can use tidyverse

library(tidyverse)
df %>%
    mutate_all(str_detect, pattern = code_regex) %>%
    reduce(`+`) %>% 
    mutate(df, indicator = .)
#  c1 c2 c3 indicator
#1 T1 R4 C5         1
#2 X1 C6 C2         0
#3 T6 C7 X4         0
#4 R5 X3 T2         1

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Or using base R

Reduce(`+`, lapply(df, grepl, pattern = code_regex))
#[1] 1 0 0 1