R help - Oct 2002 - spline bug ?

# Is this a bug or something I don't understand?
spline(date, stor, n=52, xmin=mind, xmax=maxd)
# gives length(x) of 53 ????, but y has the expected length of 52 
# Shouldn't they be the same length? From help (spline):
# spline returns a list containing components x and y which give the 
# ordinates where interpolation took place and the interpolated values

# xmin and xmax are inside min(date) and max(date) if that's important 

# If I construct the x vector separately with length 52, approx works fine 
approx(date,stor,xout=x)
# Actually, I constructed the x vector used above with:
x<-spline(date, stor, n=51, xmin=mind, xmax=maxd)$x
# note the use of 51, not 52

#Thanks, Bruce L.
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The bug reported above for "spline" is probably related to a similar
problem with sequencing in POSIX dates.
For example this works ok:
> seq(from=1,to=4,out.length=4)
 [1]  1  2  3  4 

But the following gives an output length of five, not
four:
> seq(from=ISOdate(2000,1,1),to=ISOdate(2000,1,4),length.out=4)
[1] "2000-01-01 07:00:00 EST" "2000-01-02 01:00:00 EST"
[3] "2000-01-02 19:00:00 EST" "2000-01-03 13:00:00 EST"
[5] "2000-01-04 07:00:00 EST"

Surely this is a bug?

Bruce L.
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>>>>> "Bruce" == Bruce L <mail at fwr.on.ca>
>>>>>     on Fri, 4 Oct 2002 15:17:51 -0400 writes:
    Bruce> The bug reported above for "spline" is probably related
to a similar problem with sequencing in POSIX dates.
    Bruce> For example this works ok:
    >> seq(from=1,to=4,out.length=4)
    Bruce> [1]  1  2  3  4 

    Bruce> But the following gives an output length of five, not four:
    >> seq(from=ISOdate(2000,1,1),to=ISOdate(2000,1,4),length.out=4)
    Bruce> [1] "2000-01-01 07:00:00 EST" "2000-01-02 01:00:00
EST"
    Bruce> [3] "2000-01-02 19:00:00 EST" "2000-01-03 13:00:00
EST"
    Bruce> [5] "2000-01-04 07:00:00 EST"

    Bruce> Surely this is a bug?

indeed.  Thanks a lot for reducing the problem so far!

The bug is in  seq.POSIXct()
and here is the fix -- soon to appear in "R-patched"  snapshots.

Index: src/library/base/R/datetime.R
==================================================================RCS file:
/home/rdevel/CVS-ARCHIVE/R/src/library/base/R/datetime.R,v
retrieving revision 1.35.2.1
retrieving revision 1.35.2.2
diff -w -r1.35.2.1 -r1.35.2.2
461,462c461,464
<         incr <- (to - from)/length.out
<         res <- seq.default(from, to, incr)
---
>         ## Till (and incl.) 1.6.0 :
>         ##- incr <- (to - from)/length.out
>         ##- res <- seq.default(from, to, incr)
>         res <- seq.default(from, to, length.out = length.out)
Martin Maechler <maechler at stat.math.ethz.ch>
http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO C16	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><
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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
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