[Rd] Argument recycling in substring()

Hervé Pagès hpages at fhcrc.org
Fri Jun 4 02:53:33 CEST 2010


According to its man page substring() "expands (its) arguments
cyclically to the length of the longest _provided_ none are of
zero length".

So, as expected, I get an error here:

   > substring("abcd", first=2L, last=integer(0))
   Error in substring("abcd", first = 2L, last = integer(0)) :
     invalid substring argument(s)

But I don't get one here:

   > substring(character(0), first=1:2, last=3L)

which is unexpected.

Otherwise, yes substring() will recycle its arguments to the
length of the longest:

   > substring("abcd", first=1:3, last=4:3)
   [1] "abcd" "bc"   "cd"


Hervé Pagès

Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M2-B876
P.O. Box 19024
Seattle, WA 98109-1024

E-mail: hpages at fhcrc.org
Phone:  (206) 667-5791
Fax:    (206) 667-1319

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