每n个点求和 [英] Sum every nth points

问题描述

我有一个向量，我需要对每个 n 数字求和并返回结果.这是我目前计划做的方式.有更好的方法吗?

I have a vector and I need to sum every n numbers and return the results. This is the way I plan on doing it currently. Any better way to do this?

v = 1:100
n = 10
sidx = seq.int(from=1, to=length(v), by=n)
eidx = c((sidx-1)[2:length(sidx)], length(v))
thesum = sapply(1:length(sidx), function(i) sum(v[sidx[i]:eidx[i]]))

这给出了:

thesum
 [1]  55 155 255 355 455 555 655 755 855 955

推荐答案

unname(tapply(v, (seq_along(v)-1) %/% n, sum))
# [1] 55 155 255 355 455 555 655 755 855 955 

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