[R] interpSpline with dates?

[David Winsemius]

It certainly appears that you just _did_ use it as such. You got a  
spline. The only error thrown was from predict() and I think that was  
because you needed to use a bit of extra coercion.

 > predict(sp, x=as.numeric(as.POSIXct("2008-08-02")))
$x
[1] 1217649600

$y
[1] -0.4748701

attr(,"class")
[1] "xyVector"

-- 
David Winsemius

On Feb 25, 2009, at 9:30 PM, Remko Duursma wrote:

> Dear R-helpers,
>
> can I use a POSIXct date as the x variable in interpSpline? The help
> page says x and y need to be numeric... is there a workaround?
>
> example:
>
> library(splines)
> testdfr <-  
> data.frame(Date=seq(as.POSIXct("2008-08-01"),as.POSIXct("2008-09-01"),
> length=10))
> testdfr$yvar <- rnorm(10)
> sp <- interpSpline(yvar ~ Date, testdfr)
>
> preddfr <- data.frame(Date=as.POSIXct("2008-08-02"))
> predict(sp, preddfr)
>
>
> thanks,
> Remko
>
>
> -------------------------------------------------
> Remko Duursma
> Post-Doctoral Fellow
>
> Centre for Plant and Food Science
> University of Western Sydney
> Hawkesbury Campus
> Richmond NSW 2753
>
> Dept of Biological Science
> Macquarie University
> North Ryde NSW 2109
> Australia
>
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