How to print a date when the input is number of days since 01-01-60?

I received a set of dates, but it turns out that time is reported in days since 01-01-1960 in this specific data set.

The specific date of interest for Patient 1 is 20758 days since 01-01-60

I want to create a new covariate u$date containing the specific date of interest i d%m%y%. I tried

library(tidyverse) 
u %>% mutate(date=as.date(D_INDDTO,origin="1960-01-01")

But that did not solve it.

u <- structure(list(D_INDDTO = c(20758, 20856, 21062, 19740, 21222, 
21203, 20976, 20895, 18656, 18746)), row.names = c(NA, 10L), class = "data.frame")

Solution

Try this:

#Code 1
u %>% mutate(date=as.Date("1960-01-01")+D_INDDTO)

Output:

   D_INDDTO       date
1     20758 2016-10-31
2     20856 2017-02-06
3     21062 2017-08-31
4     19740 2014-01-17
5     21222 2018-02-07
6     21203 2018-01-19
7     20976 2017-06-06
8     20895 2017-03-17
9     18656 2011-01-29
10    18746 2011-04-29

Or this:

#Code 2
u %>% mutate(date=as.Date(D_INDDTO,origin="1960-01-01"))

Output:

   D_INDDTO       date
1     20758 2016-10-31
2     20856 2017-02-06
3     21062 2017-08-31
4     19740 2014-01-17
5     21222 2018-02-07
6     21203 2018-01-19
7     20976 2017-06-06
8     20895 2017-03-17
9     18656 2011-01-29
10    18746 2011-04-29

Or this:

#Code 3
u %>% mutate(date=format(as.Date(D_INDDTO,origin="1960-01-01"),'%d%m%y'))

Output:

   D_INDDTO   date
1     20758 311016
2     20856 060217
3     21062 310817
4     19740 170114
5     21222 070218
6     21203 190118
7     20976 060617
8     20895 170317
9     18656 290111
10    18746 290411

If more customization is required:

#Code 4
u %>% mutate(date=format(as.Date(D_INDDTO,origin="1960-01-01"),'%d-%m-%Y'))

Output:

   D_INDDTO       date
1     20758 31-10-2016
2     20856 06-02-2017
3     21062 31-08-2017
4     19740 17-01-2014
5     21222 07-02-2018
6     21203 19-01-2018
7     20976 06-06-2017
8     20895 17-03-2017
9     18656 29-01-2011
10    18746 29-04-2011