R devel - Oct 2001 - seq (PR#1133)

In the following special case, seq fails to give the right answer
(which is  0 )
> seq(0,0,1)
Error in if (dd < sqrt(.Machine$double.eps)) return(from) : 
	missing value where logical needed

For any other equal  from  and  to , it works:
> seq(1,1,1)
[1] 1

The error occurs in the statement

            dd <- abs(del)/max(abs(to), abs(from))

of  seq.default  -- for obvious reasons. 
This is certainly easy to debug...

Thank you for your efforts.

Werner Stahel

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--please do not edit the information below--

Version:
 platform = i686-pc-linux-gnu
 arch = i686
 os = linux-gnu
 system = i686, linux-gnu
 status = 
 major = 1
 minor = 3.1
 year = 2001
 month = 08
 day = 31
 language = R

Search Path:
 .GlobalEnv, package:ctest, package:SfS, Autoloads, package:base

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>>>>> "Wst" == Werner Stahel
<stahel@stat.math.ethz.ch> writes:
    Wst> In the following special case, seq fails to give the right answer
    Wst> (which is  0 )

    >> seq(0,0,1)
    Wst> Error in if (dd < sqrt(.Machine$double.eps)) return(from) : 
    Wst> missing value where logical needed

    .....

    Wst> The error occurs in the statement

    Wst>     dd <- abs(del)/max(abs(to), abs(from))

    Wst> of  seq.default  -- for obvious reasons. 
    Wst> This is certainly easy to debug...
yes
    Wst> Thank you for your efforts.

Thank you, Werner!

It's now fixed for R-devel; this is the patch I've used:

--- src/library/base/R/seq.R	16 Aug 2001 14:55:20 -0000	1.14
+++ src/library/base/R/seq.R	19 Oct 2001 14:44:43 -0000
@@ -19,7 +19,9 @@
 	if(missing(by))
 	    from:to
 	else { # dealing with 'by'
-	    n <- (del <- to - from)/by
+	    del <- to - from
+	    if(del == 0 && to == 0) return(to)
+	    n <- del/by
 	    if(!(length(n) && is.finite(n))) {
 		if(length(by) && by == 0 && length(del) && del == 0)
 		    return(from)


Martin

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