Convert a date vector into Julian day in R

Question

I have a column of dates in the format: 16Jun10 and I would like to extract the Julian day. I have various years.

I have tried the functions julian and mdy.date an

Answer 1

my.data = read.table(text = "
     OBS  MONTH1  DAY1  YEAR1
       1       3     1   2012
       2       3    31   2012
       3       4     1   2012
       4       4    30   2012
       5       5     1   2012
       6       5    31   2012
       7       6     1   2012
       8       6    30   2012
       9       7     1   2012
      10       7    31   2012    
", header = TRUE, stringsAsFactors = FALSE)

my.data$MY.DATE1 <- do.call(paste, list(my.data$MONTH1, my.data$DAY1, my.data$YEAR1))
my.data$MY.DATE1 <- as.Date(my.data$MY.DATE1, format=c("%m %d %Y"))

my.data$my.julian.date <- as.numeric(format(my.data$MY.DATE1, "%j"))
my.data

Returns, which technically is incorrect since Julian dates do not return to 1 on the first day of each January:

http://en.wikipedia.org/wiki/Julian_day

The dates below are Ordinal dates:

   OBS MONTH1 DAY1 YEAR1   MY.DATE1 my.julian.date
1    1      3    1  2012 2012-03-01             61
2    2      3   31  2012 2012-03-31             91
3    3      4    1  2012 2012-04-01             92
4    4      4   30  2012 2012-04-30            121
5    5      5    1  2012 2012-05-01            122
6    6      5   31  2012 2012-05-31            152
7    7      6    1  2012 2012-06-01            153
8    8      6   30  2012 2012-06-30            182
9    9      7    1  2012 2012-07-01            183
10  10      7   31  2012 2012-07-31            213