slide_index2() and pslide_index() represent the combination of slide2() and pslide() with slide_index(), allowing you to iterate over multiple vectors at once relative to an .i-ndex.

## Usage

slide_index2(.x, .y, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

slide_index2_vec(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.ptype = NULL
)

slide_index2_dbl(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE
)

slide_index2_int(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE
)

slide_index2_lgl(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE
)

slide_index2_chr(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE
)

slide_index2_dfr(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.names_to = rlang::zap(),
.name_repair = c("unique", "universal", "check_unique")
)

slide_index2_dfc(
.x,
.y,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.size = NULL,
.name_repair = c("unique", "universal", "check_unique", "minimal")
)

pslide_index(.l, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

pslide_index_vec(
.l,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.ptype = NULL
)

pslide_index_dbl(.l, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

pslide_index_int(.l, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

pslide_index_lgl(.l, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

pslide_index_chr(.l, .i, .f, ..., .before = 0L, .after = 0L, .complete = FALSE)

pslide_index_dfr(
.l,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.names_to = rlang::zap(),
.name_repair = c("unique", "universal", "check_unique")
)

pslide_index_dfc(
.l,
.i,
.f,
...,
.before = 0L,
.after = 0L,
.complete = FALSE,
.size = NULL,
.name_repair = c("unique", "universal", "check_unique", "minimal")
)

## Arguments

.x, .y

[vector]

Vectors to iterate over. Vectors of size 1 will be recycled.

.i

[vector]

The index vector that determines the window sizes. It is fairly common to supply a date vector as the index, but not required.

There are 3 restrictions on the index:

• The size of the index must match the size of .x, they will not be recycled to their common size.

• The index must be an increasing vector, but duplicate values are allowed.

• The index cannot have missing values.

.f

[function / formula]

If a function, it is used as is.

If a formula, e.g. ~ .x + 2, it is converted to a function. There are three ways to refer to the arguments:

• For a single argument function, use .

• For a two argument function, use .x and .y

• For more arguments, use ..1, ..2, ..3 etc

This syntax allows you to create very compact anonymous functions.

...

Additional arguments passed on to the mapped function.

.before, .after

[vector(1) / function / Inf]

• If a vector of size 1, these represent the number of values before or after the current element of .i to include in the sliding window. Negative values are allowed, which allows you to "look forward" from the current element if used as the .before value, or "look backwards" if used as .after. Boundaries are computed from these elements as .i - .before and .i + .after. Any object that can be added or subtracted from .i with + and - can be used. For example, a lubridate period, such as lubridate::weeks().

• If Inf, this selects all elements before or after the current element.

• If a function, or a one-sided formula which can be coerced to a function, it is applied to .i to compute the boundaries. Note that this function will only be applied to the unique values of .i, so it should not rely on the original length of .i in any way. This is useful for applying a complex arithmetic operation that can't be expressed with a single - or + operation. One example would be to use lubridate::add_with_rollback() to avoid invalid dates at the end of the month.

The ranges that result from applying .before and .after have the same 3 restrictions as .i itself.

.complete

[logical(1)]

Should the function be evaluated on complete windows only? If FALSE, the default, then partial computations will be allowed.

.ptype

[vector(0) / NULL]

A prototype corresponding to the type of the output.

If NULL, the default, the output type is determined by computing the common type across the results of the calls to .f.

If supplied, the result of each call to .f will be cast to that type, and the final output will have that type.

If getOption("vctrs.no_guessing") is TRUE, the .ptype must be supplied. This is a way to make production code demand fixed types.

.names_to

This controls what to do with input names supplied in ....

• By default, input names are zapped.

• If a string, specifies a column where the input names will be copied. These names are often useful to identify rows with their original input. If a column name is supplied and ... is not named, an integer column is used instead.

• If NULL, the input names are used as row names.

.name_repair

One of "unique", "universal", "check_unique", "unique_quiet", or "universal_quiet". See vec_as_names() for the meaning of these options.

With vec_rbind(), the repair function is applied to all inputs separately. This is because vec_rbind() needs to align their columns before binding the rows, and thus needs all inputs to have unique names. On the other hand, vec_cbind() applies the repair function after all inputs have been concatenated together in a final data frame. Hence vec_cbind() allows the more permissive minimal names repair.

.size

If, NULL, the default, will determine the number of rows in vec_cbind() output by using the tidyverse recycling rules.

Alternatively, specify the desired number of rows, and any inputs of length 1 will be recycled appropriately.

.l

[list]

A list of vectors. The length of .l determines the number of arguments that .f will be called with. If .l has names, they will be used as named arguments to .f. Elements of .l with size 1 will be recycled.

## Value

A vector fulfilling the following invariants:

### slide_index2()

• vec_size(slide_index2(.x, .y)) == vec_size_common(.x, .y)

• vec_ptype(slide_index2(.x, .y)) == list()

### slide_index2_vec() and slide_index2_*() variants

• vec_size(slide_index2_vec(.x, .y)) == vec_size_common(.x, .y)

• vec_size(slide_index2_vec(.x, .y)[[1]]) == 1L

• vec_ptype(slide_index2_vec(.x, .y, .ptype = ptype)) == ptype

### pslide_index()

• vec_size(pslide_index(.l)) == vec_size_common(!!! .l)

• vec_ptype(pslide_index(.l)) == list()

### pslide_index_vec() and pslide_index_*() variants

• vec_size(pslide_index_vec(.l)) == vec_size_common(!!! .l)

• vec_size(pslide_index_vec(.l)[[1]]) == 1L

• vec_ptype(pslide_index_vec(.l, .ptype = ptype)) == ptype

slide2(), hop_index2(), slide_index()

## Examples

# Notice that i is an irregular index!
x <- 1:5
y <- 6:10
i <- as.Date("2019-08-15") + c(0:1, 4, 6, 7)

# When we slide over i looking back 1 day, the irregularity is respected.
# When there is a gap in dates, only 2 values are returned (one from
# x and one from y), otherwise, 4 values are returned.
slide_index2(x, y, i, ~c(.x, .y), .before = 1)
#> [[1]]
#> [1] 1 6
#>
#> [[2]]
#> [1] 1 2 6 7
#>
#> [[3]]
#> [1] 3 8
#>
#> [[4]]
#> [1] 4 9
#>
#> [[5]]
#> [1]  4  5  9 10
#>