[英]Using purrr to apply cumulative function
For each position of x, I want to count how many numbers were > 5. Here is my code, using for loop:对于 x 的每个位置,我想计算有多少个数字 > 5。这是我的代码,使用 for 循环:
x<-c(2,8,4,9,10,6,7,3,1,5)
y <- vector()
for (i in seq_along(x)) {
x1 <- x[1:i]
y <- c(y, length(x1[x1>5]))
}
> y
[1] 0 1 1 2 3 4 5 5 5 5
Can you help me do it using purrr.你能帮我用 purrr 来做吗? Can purrr::reduce be used here?这里可以使用 purrr::reduce 吗?
cumsum
function can do this cumsum
函数可以做到这一点
cumsum(x>5)
#[1] 0 1 1 2 3 4 5 5 5 5
You could use accumulate()
from purrr
:您可以使用purrr
accumulate()
:
accumulate(x > 5, `+`)
#[1] 0 1 1 2 3 4 5 5 5 5
It's basically a wrapper around Reduce()
with accumulate = TRUE
它基本上是Reduce()
一个包装器,带有accumulate = TRUE
accumulate <- function(.x, .f, ..., .init) {
.f <- as_function(.f, ...)
f <- function(x, y) {
.f(x, y, ...)
}
Reduce(f, .x, init = .init, accumulate = TRUE)
}
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