[R] Difficulty creating Julian day in data frame

[David Winsemius]

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. 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]]
>
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David Winsemius, MD
West Hartford, CT