Fixing an initial window and expanding more observations:
stretch() always returns a list.
stretch_lgl(), stretch_int(), stretch_dbl(), stretch_chr() use the same
arguments as stretch(), but return vectors of the corresponding type.
stretch_dfr() stretch_dfc() return data frames using row-binding & column-binding.
stretch(.x, .f, ..., .size = 1, .init = 1, .bind = FALSE)stretch_dfr(.x, .f, ..., .size = 1, .init = 1, .bind = FALSE,
.id = NULL)
stretch_dfc(.x, .f, ..., .size = 1, .init = 1, .bind = FALSE)
An object to slide over.
A function, formula, or atomic vector.
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.
If character vector, numeric vector, or list, it
is converted to an extractor function. Character vectors index by name
and numeric vectors index by position; use a list to index by position
and name at different levels. Within a list, wrap strings in get-attr()
to extract named attributes. If a component is not present, the value of
.default will be returned.
Additional arguments passed on to .f.
An integer for window size. If positive, moving forward from left to right; if negative, moving backward (from right to left).
A positive integer for an initial window size.
If .x is a list, should .x be combined before applying .f?
If .x is a list of data frames, row binding is carried out.
If not NULL a variable with this name will be created
giving either the name or the index of the data frame.
# NOT RUN {
x <- 1:5
lst <- list(x = x, y = 6:10, z = 11:15)
stretch_dbl(x, mean, .size = 2)
stretch_lgl(x, ~ mean(.) > 2, .size = 2)
stretch(lst, ~ ., .size = 2)
# }
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