如果我的月、日和年在不同的列中，我可以使用 R 包 lubridate 来解析日期吗？

Question

I am new at using R, but I am trying to learn how to use it to make my data analyses more reproducible. I have my dates entered in three columns for the drop off date and three columns for the pickup date (one for month, one for day, and one for year). I need to be able to get R to recognize it as a date, so I can calculate the time in field as a fraction of a year (days/365). I installed the lubridate package and tried using the mdy() function, but it gave me the following error message:

Error: Column `drop_off_date` must be length 150 (the number of rows) or one, not 450
In addition: Warning message:
All formats failed to parse. No formats found. 

I also tried using backticks, but that did not work either. I think it may be because of how my dates are set up in different columns, but I am not sure. This is the section of code I used for that:

mutate(drop_off_date = mdy(dropoff_month, dropoff_day, dropoff_year),
         pickup_date = mdy(pickup_month, pickup_day, pickup_year),

Does anyone have any suggestions for a different function or what I could fix to use this function?

Answer 1

The lubridate functions take a single vector of strings. My first comment suggested paste0 could work too, but not directly (see the code below), so you need to include a sep arator (such as paste 's default " " space).

library(lubridate)
### wrong
mdy(10, 13, 2018)
# Warning: All formats failed to parse. No formats found.
# [1] NA NA NA

### some fixed
mdy(paste(10, 13, 2018))
# [1] "2018-10-13"

library(dplyr)
data.frame(y=c(2018,2019), m=c(10,9), d=c(30,1)) %>%
  mutate(date = mdy(paste(m, d, y)))
#      y  m  d       date
# 1 2018 10 30 2018-10-30
# 2 2019  9  1 2019-09-01