simplify: Simplify a tree of delayed operations

Description Usage Arguments Details Value See Also Examples

Description

NOTE: The tools documented in this man page are primarily intended for developers or advanced users curious about the internals of the DelayedArray package. End users typically don't need them for their regular use of DelayedArray objects.

In a DelayedArray object, the delayed operations are stored as a tree of DelayedOp objects. See ?DelayedOp for more information about this tree.

simplify can be used to simplify the tree of delayed operations in a DelayedArray object.

isPristine can be used to know whether a DelayedArray object is pristine or not. A DelayedArray object is considered pristine when it carries no delayed operation. Note that an object that carries delayed operations that do nothing (e.g. A + 0) is not considered pristine.

contentIsPristine can be used to know whether the delayed operations in a DelayedArray object touch its array elements or not.

netSubsetAndAperm returns an object that represents the net subsetting and net dimension rearrangement of all the delayed operations in a DelayedArray object.

Usage

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simplify(x, incremental=FALSE)

isPristine(x, ignore.dimnames=FALSE)
contentIsPristine(x)
netSubsetAndAperm(x, as.DelayedOp=FALSE)

Arguments

x

Typically a DelayedArray object but can also be a DelayedOp object (except for isPristine).

incremental

For internal use.

ignore.dimnames

TRUE or FALSE. When TRUE, the object is considered pristine even if its dimnames have been modified and no longer match the dimnames of its seed (in which case the object carries a single delayed operations of type DelayedDimnames).

as.DelayedOp

TRUE or FALSE. Controls the form of the returned object. See details below.

Details

netSubsetAndAperm is only supported on a DelayedArray object x with a single seed i.e. if nseed(x) == 1.

The mapping between the array elements of x and the array elements of its seed is affected by the following delayed operations carried by x: [, drop(), and aperm(). x can carry any number of each of these operations in any order but their net result can always be described by a net subsetting followed by a net dimension rearrangement.

netSubsetAndAperm(x) returns an object that represents the net subsetting and net dimension rearrangement. The as.DelayedOp argument controls in what form this object should be returned:

Note that the returned object describes how the array elements of x map to their corresponding array element in seed(x).

Value

The simplified object for simplify.

TRUE or FALSE for contentIsPristine.

An ordinary list (possibly with the dimmap attribute on it) for netSubsetAndAperm. Unless as.DelayedOp is set to TRUE, in which case a DelayedAperm object is returned (see Details section above for more information).

See Also

Examples

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## ---------------------------------------------------------------------
## Simplification of the tree of delayed operations
## ---------------------------------------------------------------------
m1 <- matrix(runif(150), nrow=15, ncol=10)
M1 <- DelayedArray(m1)
showtree(M1)

## By default, the tree of delayed operations carried by a DelayedArray
## object gets simplified each time a delayed operation is added to it.
## This can be disabled via a global option:
options(DelayedArray.simplify=FALSE)
M2 <- log(t(M1[5:1, c(TRUE, FALSE)] + 10))[-1, ]
showtree(M2)  # linear tree

## Note that as part of the simplification process, some operations
## can be reordered:
options(DelayedArray.simplify=TRUE)
M2 <- log(t(M1[5:1, c(TRUE, FALSE)] + 10))[-1, ]
showtree(M2)  # linear tree

options(DelayedArray.simplify=FALSE)

dimnames(M1) <- list(letters[1:15], LETTERS[1:10])
showtree(M1)  # linear tree

m2 <- matrix(1:20, nrow=10)
Y <- cbind(t(M1[ , 10:1]), DelayedArray(m2), M1[6:15, "A", drop=FALSE])
showtree(Y)   # non-linear tree

Z <- t(Y[10:1, ])[1:15, ] + 0.4 * M1
showtree(Z)   # non-linear tree

Z@seed@seeds
Z@seed@seeds[[2]]@seed                      # reaching to M1
Z@seed@seeds[[1]]@seed@seed@seed@seed@seed  # reaching to Y

## ---------------------------------------------------------------------
## isPristine()
## ---------------------------------------------------------------------
m <- matrix(1:20, ncol=4, dimnames=list(letters[1:5], NULL))
M <- DelayedArray(m)

isPristine(M)                 # TRUE
isPristine(log(M))            # FALSE
isPristine(M + 0)             # FALSE
isPristine(t(M))              # FALSE
isPristine(t(t(M)))           # TRUE
isPristine(cbind(M, M))       # FALSE
isPristine(cbind(M))          # TRUE

dimnames(M) <- NULL
isPristine(M)                 # FALSE
isPristine(M, ignore.dimnames=TRUE)  # TRUE
isPristine(t(t(M)), ignore.dimnames=TRUE)  # TRUE
isPristine(cbind(M, M), ignore.dimnames=TRUE)  # FALSE

## ---------------------------------------------------------------------
## contentIsPristine()
## ---------------------------------------------------------------------
a <- array(1:40, c(4, 5, 2))
A <- DelayedArray(a)

stopifnot(contentIsPristine(A))
stopifnot(contentIsPristine(A[1, , ]))
stopifnot(contentIsPristine(t(A[1, , ])))
stopifnot(contentIsPristine(cbind(A[1, , ], A[2, , ])))
dimnames(A) <- list(LETTERS[1:4], letters[1:5], NULL)
stopifnot(contentIsPristine(A))

contentIsPristine(log(A))     # FALSE
contentIsPristine(A - 11:14)  # FALSE
contentIsPristine(A * A)      # FALSE

## ---------------------------------------------------------------------
## netSubsetAndAperm()
## ---------------------------------------------------------------------
a <- array(1:40, c(4, 5, 2))
M <- aperm(DelayedArray(a)[ , -1, ] / 100)[ , , 3] + 99:98
M
showtree(M)

netSubsetAndAperm(M)  # 1st dimension was dropped, 2nd and 3rd
                      # dimension were permuted (transposition)

op2 <- netSubsetAndAperm(M, as.DelayedOp=TRUE)
op2                   # 2 nested delayed operations
op1 <- op2@seed
class(op1)            # DelayedSubset
class(op2)            # DelayedAperm
op1@index
op2@perm

DelayedArray(op2)     # same as M from a [, drop(), and aperm() point of
                      # view but the individual array elements are now
                      # reset to their original values i.e. to the values
                      # they have in the seed
stopifnot(contentIsPristine(DelayedArray(op2)))

## A simple function that returns TRUE if a DelayedArray object carries
## no "net subsetting" and no "net dimension rearrangement":
is_aligned_with_seed <- function(x)
{
    if (nseed(x) != 1L)
        return(FALSE)
    op2 <- netSubsetAndAperm(x, as.DelayedOp=TRUE)
    op1 <- op2@seed
    is_noop(op1) && is_noop(op2)
}

M <- DelayedArray(a[ , , 1])
is_aligned_with_seed(log(M + 11:14) > 3)            # TRUE
is_aligned_with_seed(M[4:1, ])                      # FALSE
is_aligned_with_seed(M[4:1, ][4:1, ])               # TRUE
is_aligned_with_seed(t(M))                          # FALSE
is_aligned_with_seed(t(t(M)))                       # TRUE
is_aligned_with_seed(t(0.5 * t(M[4:1, ])[ , 4:1]))  # TRUE

options(DelayedArray.simplify=TRUE)

DelayedArray documentation built on March 25, 2021, 6:01 p.m.