Index-less Subset Methods on (Long) Vectors

The long_ - methods are similar to the ii_ - methods, except they don't require an indexing vector, and are designed for memory efficiency.

Usage

long_x(x, ...)

# Default S3 method
long_x(
  x,
  stride,
  use = 1,
  ...,
  use.names = TRUE,
  sticky = getOption("squarebrackets.sticky", FALSE)
)

long_set(x, ...)

# Default S3 method
long_set(x, stride, use = 1, ..., rp, tf)

Arguments

x: an atomic object.
For long_x(), couldb.mutatomic(x) must be TRUE.
For long_set() it must be a mutatomic variable.
...: see squarebrackets_ellipsis.
stride: see squarebrackets_stride.
use: either 1 for normal slicing, or -1 for inverted slicing.
use.names: Boolean, indicating if flat names should be preserved.
Note that, since the long_ methods operates on virtual interior indices of an array/vector only, dimensions and dimnames are always dropped.
sticky: see squarebrackets_options.
rp, tf: see squarebrackets_modify.

Value

Similar to the ii_ methods.

Examples


# extract all elements of x with the name "a":
nms <- c(letters, LETTERS, month.abb, month.name) |> rep_len(1e6)
x <- mutatomic(1:1e6, names = nms)
head(x)
#> a b c d e f 
#> 1 2 3 4 5 6 
#> mutatomic 
#> typeof:  integer 
stride <-  stride_pv(names(x), v = "a")
long_x(x, stride) |> head()
#>   a   a   a   a   a   a 
#>   1  77 153 229 305 381 
#> mutatomic 
#> typeof:  integer 


# find all x smaller than or equal to 5, and replace with `-1000`:
stride <- stride_pv(x, v = c(-Inf, 5))
long_set(x, stride, rp = -1000L)
head(x, n = 10)
#>     a     b     c     d     e     f     g     h     i     j 
#> -1000 -1000 -1000 -1000 -1000     6     7     8     9    10 
#> mutatomic 
#> typeof:  integer 




x <- mutatomic(1:1e7)

# extract elements 2 to 9
long_x(x, ~ 2:9:1)
#> [1] 2 3 4 5 6 7 8 9
#> mutatomic 
#> typeof:  integer 

# reverse:
long_x(x, ~ 9:2:1)
#> [1] 9 8 7 6 5 4 3 2
#> mutatomic 
#> typeof:  integer 

# remove:
long_x(x, ~ 1:(.N - 10):1, -1) # all elements except the last 10
#>  [1]  9999991  9999992  9999993  9999994  9999995  9999996  9999997  9999998
#>  [9]  9999999 10000000
#> mutatomic 
#> typeof:  integer 

# replace every other element:
x <- mutatomic(1:1e7)
long_set(x, ~ 2:.N:2, rp = -1)
#> coercing replacement to integer
head(x)
#> [1]  1 -1  3 -1  5 -1
#> mutatomic 
#> typeof:  integer 

# replace all elements except the first element:
x <- mutatomic(1:1e7)
long_set(x, ~1:1:1, use = -1, rp = -1)
#> coercing replacement to integer
head(x)
#> [1]  1 -1 -1 -1 -1 -1
#> mutatomic 
#> typeof:  integer 


# extract pattern c(TRUE, FALSE, FALSE, TRUE) from first 20 elements:
x <- mutatomic(1:1e7)
long_x(x, ~ 1:20:c(TRUE, FALSE, FALSE, TRUE))
#>  [1]  1  4  5  8  9 12 13 16 17 20
#> mutatomic 
#> typeof:  integer