R编程我需要帮助查找2列列表的总和

Question

我需要你的帮助：

我有一个清单：

list(c(0,1), c(1,1), c(3,2))

如何获得总和：

(0-1)+(1-1)+(3-2)

Answer 1

这可能不是计算它的最快方法，而且它肯定会使用更多的资源，但这里有一个完全不同的观点：

> mylist = list(c(0,1), c(1,1), c(3,2))

> a = matrix(unlist(mylist), ncol=2, byrow=T)
> sum(a[,1]-a[,2])

Answer 2

do.call不是Reduce的狂热粉丝，它通常更快。在这种情况下，unlist解决方案似乎有一点优势：

编辑： @ds440为胜利！

                                                  expr    min      lq median      uq     max
1     do.call(sum, lapply(List, function(z) -diff(z))) 63.132 67.7520 70.061 72.7560 291.406
2                                             ds(List)  6.930 10.5875 11.935 12.7040  51.584
3 Reduce("+", lapply(List, function(x) -sum(diff(x)))) 78.530 81.6100 83.727 87.1915 855.355
4                             sum(-sapply(List, diff)) 88.155 91.4260 94.121 97.2005 955.442
5                     sum(-unlist(lapply(List, diff))) 57.358 60.4375 61.785 63.5170 145.126

其中ds是@ds440封装在函数中的方法。

Answer 3

尝尝这个

# Sum of the first differences of your list
> (Sumlist <- lapply(List, function(x) -sum(diff(x))))
[[1]]
[1] -1    # this is (0-1)

[[2]]
[1] 0    # this is (1-1)

[[3]]
[1] 1   # this is (3-2)

# Total sum of your list
> Reduce('+', Sumlist)   # this is (0-1)+(1-1)+(3-2)
[1] 0