I think the only way that you are going to get it to stop on the first mismatch is to write your own function in C if you are concerned about the time. Matching on character vectors will be even more costly since it is having to loop to check the equality of each character in each element. This is one of the places it might pay to convert to factors and then the comparison only uses the integer values assigned to the factors.
On Tue, Jun 16, 2009 at 8:31 AM, utkarshsinghal < utkarsh.sing...@global-analytics.com> 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. > > 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> 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 >> <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> / >> />To: <vincent.gou...@act.ulaval.ca>, <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] On Behalf Of Vincent Goulet / >> />Sent: Monday, August 29, 2005 3:35 PM / >> />To: 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 >> ?Subject=Re:%20%5BR%5D%20Testing%20if%20all%20elements%20are%20equal%20in%20a%20vector/matrix> >> http://vgoulet.act.ulaval.ca / >> /> / >> />______________________________________________ / >> />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 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>/ >> >> [[alternative HTML version deleted]] >> >> >> ______________________________________________ >> 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<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? > > > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? [[alternative HTML version deleted]]
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