如何计算 R 中的天数

Question

I have this type of dataframe

DF
ID   DATE_FROM     DATE_TO
1.   01.01.2020    05.01.2020
2.   05.01.2020    11.01.2020
3.   31.01.2020    05.02.2020

We use this format of date in CZE and it means

DD.MM.YYYY

I would like to get this:

DF
ID   DATE_FROM     DATE_TO       NUM.OF.DAY
1.   01.01.2020    05.01.2020    4
2.   05.01.2020    11.01.2020    6
3.   31.01.2020    05.02.2020    5

So I would need to do basic subtraction

I tried this:

 DF %>%
   mutate(DATE_FROM = as.Date(DATE_FROM)) %>%
   mutate(DATE_TO  = as.Date(DATE_TO)) %>%
   mutate(NUM.OF.DAY = DATE_TO - DATE_FROM)

but with no result

Answer 1

You need to parse the dates and specify the format in which they are written in order to perform operations between them.

(As a side note, you can use only one mutate statement instead of three)

DF %>% 
  mutate(DATE_FROM = as.Date(DATE_FROM, format = "%d.%m.%Y"),
         DATE_TO = as.Date(DATE_TO, format = "%d.%m.%Y"),
         NUM_OF_DAY = as.numeric(DATE_TO - DATE_FROM))

Output

#   ID  DATE_FROM    DATE_TO NUM_OF_DAY
# 1  1 2020-01-01 2020-01-05          4
# 2  2 2020-01-05 2020-01-11          6
# 3  3 2020-01-31 2020-02-05          5

Answer 2

Data:

df <- data.frame(
  ID = 1,
  DATE_FROM = as.Date("01.02.2020", "%d.%m.%Y"),
  DATE_TO = as.Date("12.03.2020", "%d.%m.%Y")
)

Solution in base R :

df$NUM.OF.DAY <- as.numeric(df$DATE_TO - df$DATE_FROM)

Result:

df
  ID  DATE_FROM    DATE_TO NUM.OF.DAY
1  1 2020-02-01 2020-03-12         40

Answer 3

Another option:

difftime(as.POSIXct('12.03.2020', format = "%d.%m.%Y"), 
         as.POSIXct('01.02.2020', format = "%d.%m.%Y")
         )

#Time difference of 40 days