R help - Jan 2010 - could we use ":" to represent multiple matrice in a list or sequential chracter names

Hi,
  I know we can use 1:10 to represent the 1,2,3,...,10 numbers, but the
following conditions are except.
  Anybody knows how to represent the following two cases with similar usage
of ":"  or others? Usually, i will get several hundred names for them,
such
as a1,a2,... or f[[1]],f[[2]],...
#Example data
a1<-array(1:12,c(2,3,2)); a2<-array(2,c(2,3,2)); a3<-array(0,c(2,3,2))
a1[1,2,1]:a3[1,2,1]
[1] 3 2 1 0
#the correct result should be 3,2,0
  So the method  of using "a1[i,j,k]:a3[i,j,k]" to represent
"c(a1[i,j,k],a2[i,j,k],a3[i,j,k])" is not correct?
##For lists with matrices as its elements
f<-list()
f[[1]]<-a1;f[[2]]<-a2;f[[3]]<-a3
f[[1]][1,2,1]:f[[3]][1,2,1]
[1] 3 2 1 0
#the correct result should be 3,2,0
   So the method  of using "f[[1]][i,j,k]:f[[3]][i,j,k]" to represent
"f[[1]][i,j,k],f[[2]][i,j,k],f[[3]][i,j,k])" is not correct?
  I noticed that the above two methods have got the same results, although
not correct. So i guess i have made the same errors in them. Is there some
method to represent them concisely?
  Any ideas about them?
  Thanks a lot.


-- 
-----------------
Jane Chang
Queen's

	[[alternative HTML version deleted]]

On Jan 19, 2010, at 10:57 PM, rusers.sh wrote:
> Hi,
>  I know we can use 1:10 to represent the 1,2,3,...,10 numbers, but the
> following conditions are except.
>  Anybody knows how to represent the following two cases with similar  
> usage
> of ":"  or others? Usually, i will get several hundred names for
> them, such
> as a1,a2,... or f[[1]],f[[2]],...
> #Example data
> a1<-array(1:12,c(2,3,2)); a2<-array(2,c(2,3,2));
a3<-array(0,c(2,3,2))
 > agb <-array( , dim=c(3,2,3,2))
 > agb[1,,,] <- a1
 > agb[2,,,] <- a2
 > agb[3,,,] <- a3

 > agb[1:3 , 1, 2, 1]
[1] 3 2 0
> a1[1,2,1]:a3[1,2,1]
> [1] 3 2 1 0
> #the correct result should be 3,2,0
>  So the method  of using "a1[i,j,k]:a3[i,j,k]" to represent
> "c(a1[i,j,k],a2[i,j,k],a3[i,j,k])" is not correct?
Yes, not correct.
> ##For lists with matrices as its elements
> f<-list()
> f[[1]]<-a1;f[[2]]<-a2;f[[3]]<-a3
> f[[1]][1,2,1]:f[[3]][1,2,1]
> [1] 3 2 1 0
> #the correct result should be 3,2,0
>   So the method  of using "f[[1]][i,j,k]:f[[3]][i,j,k]" to
represent
> "f[[1]][i,j,k],f[[2]][i,j,k],f[[3]][i,j,k])" is not correct?
In both your examples the interpreter reduces the expression to 3:0  
and that results in 3 2 1 0

>  I noticed that the above two methods have got the same results,  
> although
> not correct. So i guess i have made the same errors in them. Is  
> there some
> method to represent them concisely?
>  Any ideas about them?
>  Thanks a lot.
-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

Hi:

The : operator is meant for numeric sequences; see ?':'

On Tue, Jan 19, 2010 at 7:57 PM, rusers.sh <rusers.sh@gmail.com> wrote:
> Hi,
>  I know we can use 1:10 to represent the 1,2,3,...,10 numbers, but the
> following conditions are except.
>  Anybody knows how to represent the following two cases with similar usage
> of ":"  or others? Usually, i will get several hundred names for
them, such
> as a1,a2,... or f[[1]],f[[2]],...
> #Example data
> a1<-array(1:12,c(2,3,2)); a2<-array(2,c(2,3,2));
a3<-array(0,c(2,3,2))
> a1[1,2,1]:a3[1,2,1]
> [1] 3 2 1 0
> #the correct result should be 3,2,0
>
I tried this:
> a <- list(a1, a2, a3)
> unlist(lapply(a, '[', 1, 2, 1))
[1] 3 2 0

 If you're trying to get the same element out of a bunch of arrays, this
might be one way to go.
You might also want to investigate the iapply function in the iterators
package, since it manipulates
indices in 3D arrays rather easily.

HTH,
Dennis


 So the method  of using "a1[i,j,k]:a3[i,j,k]" to
represent
> "c(a1[i,j,k],a2[i,j,k],a3[i,j,k])" is not correct?
> ##For lists with matrices as its elements
> f<-list()
> f[[1]]<-a1;f[[2]]<-a2;f[[3]]<-a3
> f[[1]][1,2,1]:f[[3]][1,2,1]
> [1] 3 2 1 0
> #the correct result should be 3,2,0
>   So the method  of using "f[[1]][i,j,k]:f[[3]][i,j,k]" to
represent
> "f[[1]][i,j,k],f[[2]][i,j,k],f[[3]][i,j,k])" is not correct?
>  I noticed that the above two methods have got the same results, although
> not correct. So i guess i have made the same errors in them. Is there some
> method to represent them concisely?
>  Any ideas about them?
>  Thanks a lot.
>
>
> --
> -----------------
> Jane Chang
> Queen's
>
>        [[alternative HTML version deleted]]
>
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