[R] date

[Val]

Hi All,

I am trying to sort dates within a group. My sample data is

df <-read.table(text="ID date
A1   09/17/04
A1   01/27/05
A1   05/07/03
A2   05/21/17
A2   09/12/16
A3   01/25/13
A4   09/27/19",header=TRUE,stringsAsFactors=F)
df$date2 = as.Date(strptime(df$date,format="%m/%d/%y"))
df$date =NULL

I want to sort  date2  from recent to oldest.  within the ID group and
I used this,
df <- df[order(df$ID, rev((df$date2))),]. It did not work and teh
output is  shown below.

ID      date2
2 A1 2005-01-27
3 A1 2003-05-07
1 A1 2004-09-17
5 A2 2016-09-12
4 A2 2017-05-21
6 A3 2013-01-25
7 A4 2019-09-27
What am I missing?
Thank you.