[tech-spec] Re: R-data objects
- From: Dirk Eddelbuettel <edd@xxxxxxxxxx>
- To: tech-spec@xxxxxxxxxxxxx
- Date: Mon, 11 Oct 2004 18:47:17 -0500
I _really_ shouldn't speak/email about this given how little I know or
understand about, but heck, one-eyed/blind/king and all that.
There are so-called S3 and S4 objects, named after the 'revisions' of the S
language. There are corresponding books by Chambers on it too.
On Mon, Oct 11, 2004 at 03:57:17PM -0700, BBands wrote:
> Version one:
> getDf <- function(file) {
> Xdata <- read.csv(file, row.names=1)
> revInd <- seq(NROW(Xdata),1)
> invisible(Xdata[revInd,])
> }
>
> IBM <- getDf("ibm.csv")
(This missed the command that actually created ibm.csv).
Here is a clue:
> class(IBM)
[1] "data.frame"
> Version two:
>
> getYahoo <- function(symbol) {
> Xdata <- priceIts(instrument = symbol, start = "2004-01-01",
> quote = c("Open", "High", "Low", "Close", "Volume", "Adj..Close."))
> }
>
> require(its)
> IBM2 <- getYahoo("IBM")
> names(IBM2) <- c("Open", "High", "Low", "Close", "Volume", "Adj..Close.")
>
> The resulting objects look the same except for the date format, but they are
> different???
Whereas:
> class(IBM2)
[1] "its"
attr(,"package")
[1] "its"
>
but using the (undocumented ?) core() function of its:
> class(core(IBM2))
[1] "matrix"
from which you can transform into a data.frame:
> class(data.frame(core(IBM2)))
[1] "data.frame"
So now IBM and IBM2 could be the same, if the start & end dates are aligned
etc pp.
> Data file attached.
It wasn't, due the amount of malware around:
> -- Binary/unsupported file stripped by Ecartis --
> -- Type: application/octet-stream
> -- File: IBM.csv
Obviously a bug in Ecartis.
Dirk
--
Those are my principles, and if you don't like them... well, I have others.
-- Groucho Marx
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