向量元素的总和 [英] Sum of vector elements

问题描述

是否可以避免使用 do 和 while 循环来计算向量元素的总和，直到出现最后一个正元素或最后一个负元素.

Is it possible to avoid using do and while loops to calculate the sum of the elements of a vector until the appearance of the last positive element or the last negative element.

推荐答案

尝试以下操作:

x <- 5:-5
# sum until last positive:
sum(x[1:max(which(x > 0))])

x <- -5:5
# sum until last negative:
sum(x[1:max(which(x < 0))])

说明:

Which(x > 0) 给出 x 大于 0 的索引号向量.取最大值给出最后一个这样的索引.然后剩下的就是将 x 从 1 加起来到这个元素.我希望这会有所帮助.

Which(x > 0) gives a vector of index numbers at which x is greater than 0. Taking the max of this gives the last such index. Then all that remains is summing up x from 1 up to this element. I hope this helps.

这篇关于向量元素的总和的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！