Find the name of the column with the minimum date using dplyr

Question

I have the following data frame, I want to find the name of the column with the minimum date for each Id. id a_date b_date c_date d_date 1 2014-01-01 2014-01-05 2014-01-15 NA 2 2017-02-01 NA NA 2015-03-01 Which is: df <- tibble(id = c(1, 2), a_date = c("01/01/14", "01/02/17"), b_date = c("05/01/14", NA), c_date = c("15/01/14", NA), d_date = c(NA, "01/03/15")) I tried this, but did not work df %>% group_by(id) %>% mutate( min = pmin(a_date, b_date, c_date, d_date ,na.rm=TRUE) %>% mutate(col_name = which(colnames(df)== min) Expected output will be as below id col_name 1 a_date 2 d_date JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

How about this? df %>% gather(key, date, -id) %>% filter(!is.na(date)) %>% mutate(date = dmy(date)) %>% group_by(id) %>% arrange(date) %>% slice(1) It produces this output: # A tibble: 2 x 3 # Groups: id [2] id key date 1 1 a_date 2014-01-01 2 2 d_date 2015-03-01