[英]Fastest way to convert a matrix to a data.table
What is the fastest way to convert a matrix like the following to a data.table?将如下矩阵转换为 data.table 的最快方法是什么?
mat <- matrix(1:9, nrow = 3)
1 2 3
4 5 6
7 8 9
I can convert this to a data.table with the code below我可以使用以下代码将其转换为 data.table
setDT(data.frame(mat))[]
But is this the fastest way?但这是最快的方法吗? Can we do this without first converting it to a data.frame?
我们可以在不先将其转换为 data.frame 的情况下做到这一点吗?
Here are some examples to discuss about the speed of forming data.table
, ie, as.data.table
, setDT(as.data.frame(mat))
and setDT(data.frame(mat))
.这里有一些例子来讨论形成
data.table
的速度,即as.data.table
, setDT(as.data.frame(mat))
和setDT(data.frame(mat))
。
mat <- matrix(1:5e3, nrow = 5)
microbenchmark(unit = "relative",
as.data.table(mat),
setDT(as.data.frame(mat))[],
setDT(data.frame(mat))[])
Unit: relative
expr min lq mean median uq max neval
as.data.table(mat) 1.433084 1.417747 1.340552 1.413278 1.414386 1.070289 100
setDT(as.data.frame(mat))[] 1.000000 1.000000 1.000000 1.000000 1.000000 1.000000 100
setDT(data.frame(mat))[] 1.287526 1.281964 1.237544 1.284735 1.258662 1.186977 100
mat <- matrix(1:5e3, nrow = 5e2)
microbenchmark(unit = "relative",
as.data.table(mat),
setDT(as.data.frame(mat))[],
setDT(data.frame(mat))[])
Unit: relative
expr min lq mean median uq max neval
as.data.table(mat) 1.114003 1.041410 1.083238 1.070029 1.049262 1.254732 100
setDT(as.data.frame(mat))[] 1.000000 1.000000 1.000000 1.000000 1.000000 1.000000 100
setDT(data.frame(mat))[] 1.680208 1.467538 1.482018 1.511009 1.479438 1.440440 100
Remark : setDT(as.data.frame(mat))[]
is the winner of speed备注:
setDT(as.data.frame(mat))[]
是速度的赢家
You could use a magrittr
pipe:您可以使用
magrittr
pipe:
mat <- matrix(1:9, nrow = 3) %>% data.table()
Without magrittr
:没有
magrittr
:
mat <- data.table(matrix(1:9, nrow = 3))
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