R foreach 与 .combine=rbindlist [英] R foreach with .combine=rbindlist

问题描述

我正在使用带有 .combine = rbindlist 的 foreach.这似乎不起作用，尽管如果我使用 .combine = rbind 可以正常工作.

I am using foreach with a .combine = rbindlist. This does not appear to work, although it works fine if I use .combine = rbind.

只是用一个简单的例子来说明--

Just to illustrate using a simple example --

> t2 <- data.table(col1=c(1,2,3))
> foreach (i=1:3, .combine=rbind) %dopar% unique(t2)
   col1
1:    1
2:    2
3:    3
4:    1
5:    2
6:    3
7:    1
8:    2
9:    3

# But using rbindlist gives an error

> foreach (i=1:3, .combine=rbindlist) %dopar% unique(t2)
error calling combine function:
<simpleError in fun(result.1, result.2): unused argument(s) (result.2)>
NULL

有人能做到吗?

提前致谢.

推荐答案

基本上就是你所说的 - rbindlist 假定一个 list 参数，并且你得到的错误和这个一样:

It's basically what you said - rbindlist assumes a list argument, and the error you're getting is the same as this one:

result.1 = data.table(blah = 23)
result.2 = data.table(blah = 34)

rbindlist(result.1, result.2)
#Error in rbindlist(result.1, result.2) : unused argument (result.2)

如果你想使用rbindlist，方法是这样的:

If you want to utilize rbindlist, the way to do it would be this:

rbindlist(foreach (i = 1:3) %dopar% unique(t2))

或者这个:

foreach (i=1:3, .combine=function(x,y)rbindlist(list(x,y))) %dopar% unique(t2)

这篇关于R foreach 与 .combine=rbindlist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！