R help - Dec 2004 - test multiple objects for being equal length

I could not find any help pages on How to test many
objects for being of equal length
Something like identical for more than two objects?
x<-1:6
y<-1:10
z<-3:5
## For two objects I can do:
identical(length(x),length(y))
## For more than two I currently can do:
length(unique(c(length(x),length(y),length(z))))==1

but there must be a better way.
Thanks,
M

Hi Manuel,

First, encapsulate yoyr objects within a list. That will help you 
manipulate all them at once and ensures that the final function will work 
with whatever number of vectors.

?? ll <- list(x,y,z)
?? sapply(ll,length)
[1]  6 10  3

Then you can use your length(unique(...))==1
Another way is to use all:

?? all(sapply(ll,length)==length(ll[[1]]))
[1] FALSE

HTH,

Eric



At 09:09 9/12/2004, Manuel Gutierrez wrote:
>I could not find any help pages on How to test many
>objects for being of equal length
>Something like identical for more than two objects?
>x<-1:6
>y<-1:10
>z<-3:5
>## For two objects I can do:
>identical(length(x),length(y))
>## For more than two I currently can do:
>length(unique(c(length(x),length(y),length(z))))==1
>
>but there must be a better way.
>Thanks,
>M
>
>______________________________________________
>R-help at 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
Eric Lecoutre
UCL /  Institut de Statistique
Voie du Roman Pays, 20
1348 Louvain-la-Neuve
Belgium

tel: (+32)(0)10473050
lecoutre at stat.ucl.ac.be
http://www.stat.ucl.ac.be/ISpersonnel/lecoutre

If the statistics are boring, then you've got the wrong numbers. -Edward 
Tufte

not that its much shorter:

length( table( sapply( list(x,y,z), length ) ) ) == 1

Bendix
----------------------
Bendix Carstensen
Senior Statistician
Steno Diabetes Center
Niels Steensens Vej 2
DK-2820 Gentofte
Denmark
tel: +45 44 43 87 38
mob: +45 30 75 87 38
fax: +45 44 43 07 06
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----------------------


> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Manuel 
> Gutierrez
> Sent: Thursday, December 09, 2004 9:09 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] test multiple objects for being equal length
> 
> 
> I could not find any help pages on How to test many
> objects for being of equal length
> Something like identical for more than two objects?
> x<-1:6
> y<-1:10
> z<-3:5
> ## For two objects I can do:
> identical(length(x),length(y))
> ## For more than two I currently can do: 
> length(unique(c(length(x),length(y),length(z))))==1
> 
> but there must be a better way.
> Thanks,
> M
> 
> ______________________________________________
> R-help at 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
>

Wrapping the suggestions into a function:
> sameLength <- function(...) {
+     n <- sapply(list(...), length)
+     all(n == n[1])
+ }
> sameLength(double(1), double(2))
[1] FALSE
> sameLength(double(1), double(1), list(x=1))
[1] TRUE

[Note that if you have lots of objects to compare, length(unique(...))==1
will not be as efficient.]

HTH,
Andy

> From: Manuel Gutierrez
> 
> I could not find any help pages on How to test many
> objects for being of equal length
> Something like identical for more than two objects?
> x<-1:6
> y<-1:10
> z<-3:5
> ## For two objects I can do:
> identical(length(x),length(y))
> ## For more than two I currently can do:
> length(unique(c(length(x),length(y),length(z))))==1
> 
> but there must be a better way.
> Thanks,
> M
> 
> ______________________________________________
> R-help at 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
> 
>