On Tue, 17 Nov 2009, Bryan Hanson wrote:
Patrick reminded me that it's also in The R Inferno, another document that I
need to read again.
So now, a more particular semi-question:
x <- 1L
y <- 1
z <- 1.0
class(x) # integer
class(y) # numeric
class(z) # numeric
NB: identical(x, y) is TRUE, so they behave the same.
x == 1
x == 1L
y == 1
z == 1 # all test TRUE
Just to clarify, I think the steps above prove it, but *in a test* like x ==
1 the test is for the contents, not the storage mode, not for a combination
of storage mode and contents.
Not really: the operands are coerced to a common type and then tested
for equality. From the help page for "=="
If the two arguments are atomic vectors of different types, one is
coerced to the type of the other, the (decreasing) order of
precedence being character, complex, numeric, integer, logical and
raw.
So... The reason for defining the notion of "L" is smaller storage space,
and more generally, for use anytime one wants explictly an integer for
whatever reason? Are there other reasons, for instance, ways it saves lines
of code?
It avoids coercion. The test x == 1 requires x to be coerced from
integer to double, and foo[1] requires '1' to be coerced from double
to integer. There is little if any gain in storage space for small
integer vectors over small double vectors, but all those coercions can
create a lot of new objects which need to be garbage-collected.
Also, 2L is simpler to write and to read than as.integer(2) (and
avoids a funtion call and a coercion).
Bryan
*************
Bryan Hanson
Acting Chair
Professor of Chemistry & Biochemistry
DePauw University, Greencastle IN USA
On 11/17/09 4:20 AM, "Patrick Burns" <pbu...@pburns.seanet.com> wrote:
'The R Inferno' page 75.
Patrick Burns
patr...@burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of "The R Inferno" and "A Guide for the Unwilling S User")
Bryan Hanson wrote:
Gurus:
I keep seeing other people¹s code that contain ideas like
If (x == 2L)
X[-1L]
X - 1L
I have some idea of what¹s going on, but where is the use of concepts like
³2L² documented?
Thanks, Bryan
*************
Bryan Hanson
Acting Chair
Professor of Chemistry & Biochemistry
DePauw University, Greencastle IN USA
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
