[R] Difficulty creating Julian day in data frame

[David Winsemius]

On Sep 15, 2010, at 12:23 PM, David Winsemius wrote:

>
> On Sep 15, 2010, at 12:05 PM, Sean Parks wrote:
>
>> Hi,
>>
>> I'm attempting to add a "Julian Day" column to a data frame.
>>
>> Here is my code and the resulting data frame:
>>
>>       vic.data <- read.table("C:/VIC/data/vic.data.csv", header=F)
>>       names(vic.data) <- c("year", "month", "day", "precip", "evap",
>> "runoff", "baseflow", "Tsup", "SM1", "SM2", "SM3", "SWE")
>>
>>
>
>
>>       vic.data$julian.day <- julian(vic.data$temp.date, origin =
>> as.Date("1900-01-01"))[1]
>
> There's one problem. Why are you appending the "[1]? to the as.Date  
> function.

Er, ... that would be the julian function. (But same import.)
-- David
> It's just going to give you the first date.
> -- 
> David.
>
>>       head(vic.data)
>>
>> year month day precip   evap runoff baseflow     Tsup     SM1     SM2
>> SM3      SWE  temp.date julian.day
>> 1 1916     1   1   0.00 0.0789      0   0.5037 -15.9907 20.2285  
>> 63.4011
>> 296.9437 214.7537 1916-01-01       5843
>> 2 1916     1   2   0.00 0.1135      0   0.5030 -14.1946 20.1619  
>> 63.3425
>> 296.5659 214.7009 1916-01-02       5843
>> 3 1916     1   3  29.74 0.1584      0   0.5024 -11.1894 20.0998  
>> 63.2817
>> 296.1864 244.0971 1916-01-03       5843
>> 4 1916     1   4  11.37 0.2056      0   0.5017 -12.9745 20.0416  
>> 63.2194
>> 295.8052 255.3145 1916-01-04       5843
>> 5 1916     1   5   0.00 0.1467      0   0.5011 -15.1542 19.9866  
>> 63.1561
>> 295.4224 255.2361 1916-01-05       5843
>> 6 1916     1   6   0.00 0.0939      0   0.5004 -12.5409 19.9345  
>> 63.0922
>> 295.0379 255.2084 1916-01-06       5843
>>
>>
>> As you can see, the "temp.date" column behaves as expected, but the
>> "julian.day" column is populated with the Julian day value from  
>> 1/1/1916.
>>
>> Please help me out if you have some ideas.
>>
>> Thanks,
>> Sean
>>
>>
>>
>>
>> *************************
>> Sean Parks
>> Ecologist | Geospatial Analyst
>> Aldo Leopold Wilderness Research Institute
>> Rocky Mountain Research Station
>> (406) 542-4182
>> http://leopold.wilderness.net/
>> *************************
>> 	[[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT