Convert Julian date to calendar dates within a data frame

Question

I have a data frame

> df
Age   year  sex
12    80210  F
13     9123  M

I want to convert the year 80210 as 26june1982. How can I do this t

Answer 1

You should substract the origin from the year column.

 as.Date(c(80210,9123)-80210,origin='1982-06-26')
[1] "1982-06-26" "1787-11-08"

Answer 2

You can convert Julian dates to dates using as.Date and specifying the appropriate origin:

as.Date(8210, origin=as.Date("1960-01-01"))
#[1] "1982-06-24"

However, 80210 needs an origin pretty long ago.

Answer 3

There are some options for doing this job in the R package date.

See for example on page 4, the function date.mmddyy, which says:

Given a vector of Julian dates, this returns them in the form “10/11/89”, “28/7/54”, etc.

Try this code:

age = c(12,13)
year = c(8210,9123)
sex = c("F","M")

df = data.frame(cbind(age,year,sex))

library(date)
date = date.mmddyy(year, sep = "/")

df2 = transform(df,year=date) #hint provided by jilber
df2

  age     year sex
1  12  6/24/82   F
2  13 12/23/84   M