Re: [R] List to Array: How to establish the dimension of the array
Please include the context of the discussion in your responses. See
inline below.
On 1/24/2012 11:33 PM, Ajay Askoolum wrote:
Thanks you,
I can get the length of aa with length(unlist(aa)). If aa has 4
dimensions, I imagine I'd need to do
max(sapply(aa,sapply,sapply,length)
Correct.
How can I do this in a generic way? That is in a loop. I am clear
about the exit condition for the loop.
By generic, I assume that you mean without knowing the depth of the
lists (that is, "dimensions") to begin with?
d<-1
start loop
if d = length(unlist(aa)) then exit loop
Note that length(unlist(aa)) will only equal the product of the
dimensions if the data is "regular." That is, there is an entry for
every combination of indices (within the dimensions).
else
d<-d *
How do I construct such that it does
d<- d * length(aa) # first pass
d<- d * max(sapply(aa, length)) # second pass
d<- d * max(sapply(aa, sapply, length)) # third pass
# ? ## fourth path etc
(Apologies for the pseudo code describing the loop; I am not near a
machine with R)
I don't really understand this.
One way I can thing of is to create a loop counter variable, say
lc<-1 and to increment it within the loop and then use a switch
statement to execute the appropriate expression. This sems like a
kludge to me.
Is there a neater way?
If you are trying to get back a vector of the dimensions, then this
would work:
dimRecursiveList <- function(l) {
if (class(l) == "list") {
c(length(l), dimRecursiveList(l[[1]]))
} else {
NULL
}
}
From previous context:
aa <- list(list(list(37531.52, 62787.32, 5503.184, 33832.8),
list(20469.60, 27057.27, 51160.25, 45165.24),
list(957.932, 21902.94, 37531.52, 62787.32)),
list(list(5503.184, 33832.8, 20469.6, 27057.27),
list(51160.25, 45165.24, 957.932, 21902.94),
list(37531.52, 62787.32, 5503.184, 33832.8)))
Which then gives
> dimRecursiveList(aa)
[1] 2 3 4
In this case, the data is regular, so
> Reduce(`*`, dimRecursiveList(aa)) == length(unlist(aa))
[1] TRUE
If the data are not regular, and you want the dimension to be the
largest, then it is more complicated (due to bookkeeping)
dimRecursiveListIrregular <- function(l) {
if (class(l) == "list") {
dims <- sapply(l, dimRecursiveListIrregular)
if (is.null(dim(dims))) {
if (all(is.na(dims))) {
length(l)
} else {
c(length(l), max(dims, na.rm=TRUE))
}
} else {
c(length(l), apply(dims, 1, max, na.rm=TRUE))
}
} else {
NA
}
}
If the data are regular, then it is better to convert this to an array.
This function will do it for arbitrary depth
RecursiveListToArray <- function(l) {
if(class(l) == "list") {
laply(l, RecursiveListToArray)
} else {
l
}
}
> aaa <- RecursiveListToArray(aa)
> dim(aaa)
[1] 2 3 4
--
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University
__
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Re: [R] List to Array: How to establish the dimension of the array
Hello,
If you just want the dimensions of the array, and assuming the input list
will give
a rectangular array with no need to use NA's, the function below works.
(It doesn't construct the array)
aa <- list(list(list(1:4),
list(5:8),
list(9:12)),
list(list(13:16),
list(17:20),
list(21:24)))
bb <- list(aa, aa, aa, aa, aa)
fun <- function(lst){
d <- ix <- 0
while(length(lst) > 1){
d[ix <- ix+1] <- length(lst)
lst <- lst[[1]]
}
d[ix+1] <- length(lst[[1]])
d
}
fun(aa)
fun(bb)
fun(list(aa, bb)) # not rectangular, therefore
fun(list(bb, aa)) # different results
Rui Barradas
--
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Re: [R] List to Array: How to establish the dimension of the array
Thanks you, I can get the length of aa with length(unlist(aa)). If aa has 4 dimensions, I imagine I'd need to do max(sapply(aa,sapply,sapply,length) How can I do this in a generic way? That is in a loop. I am clear about the exit condition for the loop. d<-1 start loop if d = length(unlist(aa)) then exit loop else d<-d * How do I construct such that it does > d<- d * length(aa) # first pass > d<- d * max(sapply(aa, length)) # second pass > d<- d * max(sapply(aa, sapply, length)) # third pass > # ? # # fourth path etc (Apologies for the pseudo code describing the loop; I am not near a machine with R) One way I can thing of is to create a loop counter variable, say lc<-1 and to increment it within the loop and then use a switch statement to execute the appropriate expression. This sems like a kludge to me. Is there a neater way? [[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 and provide commented, minimal, self-contained, reproducible code.
Re: [R] List to Array: How to establish the dimension of the array
On 1/24/2012 2:47 PM, Ajay Askoolum wrote:
Given a variable aa in the workspace, some of its attributes are:
typeof(aa)
[1] "list"
mode(aa)
[1] "list"
length(aa)
[1] 2
How do I retrieve the maximum indices, in this case 2,3,4? The variable itself
is:
aa
[[1]]
[[1]][[1]]
[[1]][[1]][[1]]
[1] 37531.52
[[1]][[1]][[2]]
[1] 62787.32
[[1]][[1]][[3]]
[1] 5503.184
[[1]][[1]][[4]]
[1] 33832.8
[[1]][[2]]
[[1]][[2]][[1]]
[1] 20469.6
[[1]][[2]][[2]]
[1] 27057.27
[[1]][[2]][[3]]
[1] 51160.25
[[1]][[2]][[4]]
[1] 45165.24
[[1]][[3]]
[[1]][[3]][[1]]
[1] 957.932
[[1]][[3]][[2]]
[1] 21902.94
[[1]][[3]][[3]]
[1] 37531.52
[[1]][[3]][[4]]
[1] 62787.32
[[2]]
[[2]][[1]]
[[2]][[1]][[1]]
[1] 5503.184
[[2]][[1]][[2]]
[1] 33832.8
[[2]][[1]][[3]]
[1] 20469.6
[[2]][[1]][[4]]
[1] 27057.27
[[2]][[2]]
[[2]][[2]][[1]]
[1] 51160.25
[[2]][[2]][[2]]
[1] 45165.24
[[2]][[2]][[3]]
[1] 957.932
[[2]][[2]][[4]]
[1] 21902.94
[[2]][[3]]
[[2]][[3]][[1]]
[1] 37531.52
[[2]][[3]][[2]]
[1] 62787.32
[[2]][[3]][[3]]
[1] 5503.184
[[2]][[3]][[4]]
[1] 33832.8
[[alternative HTML version deleted]]
Better to give the dput version of aa, so that it can be recreated easily
aa <- list(list(list(37531.52, 62787.32, 5503.184, 33832.8),
list(20469.60, 27057.27, 51160.25, 45165.24),
list(957.932, 21902.94, 37531.52, 62787.32)),
list(list(5503.184, 33832.8, 20469.6, 27057.27),
list(51160.25, 45165.24, 957.932, 21902.94),
list(37531.52, 62787.32, 5503.184, 33832.8)))
Given that, the three "dimensions" can be gotten with
length(aa)
max(sapply(aa, length))
max(sapply(aa, sapply, length))
which give
> length(aa)
[1] 2
> max(sapply(aa, length))
[1] 3
> max(sapply(aa, sapply, length))
[1] 4
If you want to turn this into an actual array (assuming it is regular),
you can do that fairly easily with the plyr package
(I imagine you can do it with base functions too, but in a quick attempt
was not able to do so).
library("plyr")
aaa <- laply(aa, laply, laply, identity)
Then all the dimensions can be gotten at once
> dim(aaa)
[1] 2 3 4
--
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University
__
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] List to Array: How to establish the dimension of the array
Given a variable aa in the workspace, some of its attributes are: > typeof(aa) [1] "list" > mode(aa) [1] "list" > length(aa) [1] 2 How do I retrieve the maximum indices, in this case 2,3,4? The variable itself is: > aa [[1]] [[1]][[1]] [[1]][[1]][[1]] [1] 37531.52 [[1]][[1]][[2]] [1] 62787.32 [[1]][[1]][[3]] [1] 5503.184 [[1]][[1]][[4]] [1] 33832.8 [[1]][[2]] [[1]][[2]][[1]] [1] 20469.6 [[1]][[2]][[2]] [1] 27057.27 [[1]][[2]][[3]] [1] 51160.25 [[1]][[2]][[4]] [1] 45165.24 [[1]][[3]] [[1]][[3]][[1]] [1] 957.932 [[1]][[3]][[2]] [1] 21902.94 [[1]][[3]][[3]] [1] 37531.52 [[1]][[3]][[4]] [1] 62787.32 [[2]] [[2]][[1]] [[2]][[1]][[1]] [1] 5503.184 [[2]][[1]][[2]] [1] 33832.8 [[2]][[1]][[3]] [1] 20469.6 [[2]][[1]][[4]] [1] 27057.27 [[2]][[2]] [[2]][[2]][[1]] [1] 51160.25 [[2]][[2]][[2]] [1] 45165.24 [[2]][[2]][[3]] [1] 957.932 [[2]][[2]][[4]] [1] 21902.94 [[2]][[3]] [[2]][[3]][[1]] [1] 37531.52 [[2]][[3]][[2]] [1] 62787.32 [[2]][[3]][[3]] [1] 5503.184 [[2]][[3]][[4]] [1] 33832.8 [[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 and provide commented, minimal, self-contained, reproducible code.
