iarray: Create an iterator over an array

In itertools: Iterator Tools

Description

Create an iterator over an array.

Usage

iarray(X, MARGIN, ..., chunks, chunkSize, drop,
       idx=lapply(dim(X), function(i) TRUE))

Arguments

X	Array to iterate over.
MARGIN	Vector of subscripts to iterate over. Note that if the length of MARGIN is greater than one, the resulting iterator will generate iterators which is particularly useful with nested foreach loops.
...	Used to force subsequent arguments to be specified by name.
chunks	Number of elements that the iterator should generate. This can be a single value or a vector the same length as MARGIN. A single value will be recycled for each dimension if MARGIN has more than one value.
chunkSize	The maximum size Number of elements that the iterator should generate. This can be a single value or a vector the same length as MARGIN. A single value will be recycled for each dimension if MARGIN has more than one value.
drop	Should dimensions of length 1 be dropped in the generated values? It defaults to FALSE if either chunks or chunkSize is specified, otherwise to TRUE.
idx	List of indices used to generate a call object.

See Also

apply

Examples

  # Iterate over matrices in a 3D array
  x <- array(1:24, c(2,3,4))
  as.list(iarray(x, 3))

  # Iterate over subarrays
  as.list(iarray(x, 3, chunks=2))

  x <- array(1:64, c(4,4,4))
  it <- iarray(x, c(2,3), chunks=c(1,2))
  jt <- nextElem(it)
  nextElem(jt)
  jt <- nextElem(it)
  nextElem(jt)

  it <- iarray(x, c(2,3), chunks=c(2,2))
  jt <- nextElem(it)
  nextElem(jt)
  nextElem(jt)
  jt <- nextElem(it)
  nextElem(jt)
  nextElem(jt)

Example output

Loading required package: iterators
[[1]]
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

[[2]]
     [,1] [,2] [,3]
[1,]    7    9   11
[2,]    8   10   12

[[3]]
     [,1] [,2] [,3]
[1,]   13   15   17
[2,]   14   16   18

[[4]]
     [,1] [,2] [,3]
[1,]   19   21   23
[2,]   20   22   24

[[1]]
, , 1

     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

, , 2

     [,1] [,2] [,3]
[1,]    7    9   11
[2,]    8   10   12


[[2]]
, , 1

     [,1] [,2] [,3]
[1,]   13   15   17
[2,]   14   16   18

, , 2

     [,1] [,2] [,3]
[1,]   19   21   23
[2,]   20   22   24


, , 1

     [,1] [,2] [,3] [,4]
[1,]    1    5    9   13
[2,]    2    6   10   14
[3,]    3    7   11   15
[4,]    4    8   12   16

, , 2

     [,1] [,2] [,3] [,4]
[1,]   17   21   25   29
[2,]   18   22   26   30
[3,]   19   23   27   31
[4,]   20   24   28   32

, , 1

     [,1] [,2] [,3] [,4]
[1,]   33   37   41   45
[2,]   34   38   42   46
[3,]   35   39   43   47
[4,]   36   40   44   48

, , 2

     [,1] [,2] [,3] [,4]
[1,]   49   53   57   61
[2,]   50   54   58   62
[3,]   51   55   59   63
[4,]   52   56   60   64

, , 1

     [,1] [,2]
[1,]    1    5
[2,]    2    6
[3,]    3    7
[4,]    4    8

, , 2

     [,1] [,2]
[1,]   17   21
[2,]   18   22
[3,]   19   23
[4,]   20   24

, , 1

     [,1] [,2]
[1,]    9   13
[2,]   10   14
[3,]   11   15
[4,]   12   16

, , 2

     [,1] [,2]
[1,]   25   29
[2,]   26   30
[3,]   27   31
[4,]   28   32

, , 1

     [,1] [,2]
[1,]   33   37
[2,]   34   38
[3,]   35   39
[4,]   36   40

, , 2

     [,1] [,2]
[1,]   49   53
[2,]   50   54
[3,]   51   55
[4,]   52   56

, , 1

     [,1] [,2]
[1,]   41   45
[2,]   42   46
[3,]   43   47
[4,]   44   48

, , 2

     [,1] [,2]
[1,]   57   61
[2,]   58   62
[3,]   59   63
[4,]   60   64

itertools documentation built on May 2, 2019, 2:26 p.m.