datetime - How to convert Dates to Quarters in R -

i have panel data set in below format

individual    date             05/10/2010             06/11/2011             21/07/2012 b             22/02/2010 b             15/03/2011 b             28/09/2012 

i want convert date quarters such quarter 2010 should 1,2,3,4....and quarter 2011 should start 5 until 8...and quarter 2012 should start 9 until 12.

can please suggest code in r?

library(zoo) df$date <- strptime(df$date, "%d/%m/%y") x <- as.numeric(as.yearqtr(df$date)) firstyr <- as.numeric(as.character(strftime(min(df$date), "%y"))) df$quarter <- (x-(firstyr-1))/.25-3 #   individual       date quarter # 1          05/10/2010       4 # 2          06/11/2011       8 # 3          21/07/2012      11 # 4          b 22/02/2010       1 # 5          b 15/03/2011       5 # 6          b 28/09/2012      11 

data

df <- read.table(text="    individual    date                 05/10/2010                 06/11/2011                 21/07/2012     b             22/02/2010     b             15/03/2011     b             28/09/2012", header=t)