utkarshsinghal wrote:
Hi Jim,
What you are saying is correct. Although, my computer might not have
same speed and I am getting the following for 10M entries:
user system elapsed
0.559 0.038 0.607
Moreover, in the case of character vectors, it gets more than double.
In my modeling, which is already highly time consuming, I need to do
check this for few thousand vectors and the entries can easily be 10M in
each vector. So I am just looking for any possibilities of time saving.
I am pretty sure that whenever elements are not all equal, it can be
concluded from any few entries (most of the times). It will be worth if
I can find a way which stops checking further the moment it find two
distinct elements.
*very* naively, you could define a tunable length to test only the first
few lines of each vector first. It's probably only useful if you have a
good guess on the likelihood of non-identity within the first n entries,
testTwoStages <- function(x= 1:10, y= rep(1,100), head.stop = 3){
if(!isTRUE(all(head(x, head.stop) == head(y, head.stop))))
{
print(paste("quick test returned FALSE"))
return(FALSE)
} else {
print(paste("full test returned FALSE"))
return(identical(tail(x, length(x) - head.stop), tail(y, length(y) -
head.stop)))}
}
x <- seq(1, 1e6)
y <- x
y[325] <- 0
> system.time(testTwoStages(x, y))
[1] "full test returned FALSE"
user system elapsed
0.128 0.072 0.204
> system.time(testTwoStages(x, y, 400))
[1] "quick test returned FALSE"
user system elapsed
0.006 0.001 0.008
HTH,
baptiste
Regards
Utkarsh
jim holtman wrote:
Just check that the first (or any other element) is equal to all the rest:
x = c(1,2,rep(1,10000000)) # 10,000,000
system.time(print(all(x[1] == x)))
[1] FALSE
user system elapsed
0.18 0.00 0.19
This was for 10M entries.
On Tue, Jun 16, 2009 at 7:42 AM, utkarshsinghal
<utkarsh.sing...@global-analytics.com
<mailto:utkarsh.sing...@global-analytics.com>> wrote:
Hi All,
There are several replies to the question below, but I think there
must
exist a better way of doing so.
I just want to check whether all the elements of a vector are same. My
vector has one million elements and it is highly likely that there are
distinct elements in the first few itself. For example:
> x = c(1,2,rep(1,100000))
I want the answer as FALSE, which is clear from the first two
observations itself and we don't need to check for the rest.
Does anybody know the most efficient way of doing this?
Regards
Utkarsh
From: Francisco J. Zagmutt <gerifalte28_at_hotmail.com
<http://gerifalte28_at_hotmail.com/>
<mailto:gerifalte28_at_hotmail.com
<mailto:gerifalte28_at_hotmail.com>?Subject=Re:%20%5BR%5D%20Testing%20if%20all%20elements%20are%20equal%20in%20a%20vector/matrix>>
Date: Tue 30 Aug 2005 - 06:05:20 EST
Hi Doran
The documentation for isTRUE reads 'isTRUE(x)' is an abbreviation of
'identical(TRUE,x)' so actually Vincent's solutions is "cleaner" than
using identical :)
Cheers
Francisco
/>From: "Doran, Harold" <hdo...@air.org <mailto:hdo...@air.org>> /
/>To: <vincent.gou...@act.ulaval.ca
<mailto:vincent.gou...@act.ulaval.ca>>, <r-h...@stat.math.ethz.ch
<mailto:r-h...@stat.math.ethz.ch>> /
/>Subject: Re: [R] Testing if all elements are equal in a
vector/matrix /
/>Date: Mon, 29 Aug 2005 15:49:20 -0400 /
/> /
>See ?identical
<http://tolstoy.newcastle.edu.au/R/help/05/08/11201.html#11202qlink1>
/> /
/>-----Original Message----- /
/>From: r-help-boun...@stat.math.ethz.ch
<mailto:r-help-boun...@stat.math.ethz.ch> /
/>[mailto:r-help-boun...@stat.math.ethz.ch
<mailto:r-help-boun...@stat.math.ethz.ch>] On Behalf Of Vincent
Goulet /
/>Sent: Monday, August 29, 2005 3:35 PM /
/>To: r-h...@stat.math.ethz.ch <mailto:r-h...@stat.math.ethz.ch> /
/>Subject: [R] Testing if all elements are equal in a vector/matrix /
/> /
/> /
/>Is there a canonical way to check if all elements of a vector or
matrix are /
/>the same? Solutions below work, but look hackish to me. /
/> /
/> > x <- rep(1, 10) /
/> > all(x == x[1]) # == operator does not provide for small
differences /
*/>[1] TRUE /
*/> > isTRUE(all.equal(x, rep(x[1], length(x)))) # ugly /
*/>[1] TRUE /
*/> /
/>Best, /
/> /
/>Vincent /
/>-- /
/> Vincent Goulet, Associate Professor /
/> École d'actuariat /
/> Université Laval, Québec /
/> Vincent.Goulet_at_act.ulaval.ca
<http://vincent.goulet_at_act.ulaval.ca/>
<mailto:Vincent.Goulet_at_act.ulaval.ca
<mailto:Vincent.Goulet_at_act.ulaval.ca>?Subject=Re:%20%5BR%5D%20Testing%20if%20all%20elements%20are%20equal%20in%20a%20vector/matrix>
http://vgoulet.act.ulaval.ca <http://vgoulet.act.ulaval.ca/> /
/> /
/>______________________________________________ /
/>r-h...@stat.math.ethz.ch <mailto:r-h...@stat.math.ethz.ch>
mailing list /
/>https://stat.ethz.ch/mailman/listinfo/r-help /
/>PLEASE do read the posting guide! /
/>http://www.R-project.org/posting-guide.html
<http://www.r-project.org/posting-guide.html> /
/> /
/>______________________________________________ /
/>r-h...@stat.math.ethz.ch <mailto:r-h...@stat.math.ethz.ch>
mailing list /
/>https://stat.ethz.ch/mailman/listinfo/r-help /
/>PLEASE do read the posting guide! /
/>http://www.R-project.org/posting-guide.html
<http://www.r-project.org/posting-guide.html> /
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PLEASE do read the posting guide
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<http://www.r-project.org/posting-guide.html>
and provide commented, minimal, self-contained, reproducible code.
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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------------------------------------------------------------------------
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
______________________________________________
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