r - 将环境中的所有data.frames转换为data.tables

Question

将所有data.frames转换为data.tables之后立即使用:=时，我会收到警告:

library(data.table) #Win R-3.5.1 x64 data.table_1.12.2
df1 <- data.frame(A=1, B=2)
df2 <- data.frame(D=3)
lapply(mget(ls()), function(x) {
    if (is.data.frame(x)) {
        setDT(x)
    }
})
df1[, rn:=.I]

Warning message: In [.data.table(df1, , :=(rn, .I)) : Invalid .internal.selfref detected and fixed by taking a (shallow) copy of the data.table so that := can add this new column by reference. At an earlier point, this data.table has been copied by R (or was created manually using structure() or similar). Avoid names<- and attr<- which in R currently (and oddly) may copy the whole data.table. Use set* syntax instead to avoid copying: ?set, ?setnames and ?setattr. If this message doesn't help, please report your use case to the data.table issue tracker so the root cause can be fixed or this message improved.

下面还生成了相同的警告:

df3 <- data.frame(E=3)
df4 <- data.frame(FF=4)
for (l in list(df3, df4)) setDT(l)
df3[, rn:=.I]

一一打字很乏味

df5 <- data.frame(G=5)
setDT(df5)
df[, rn := .I]    #no warning

将所有data.frames转换为data.tables的惯用方式是什么？

有关的:

Using setDT inside a function

Invalid .internal.selfref in data.table

Answer 1

有点晚了，但是使用eapply()(以及list2env())似乎是一种很棒的方法，并且很少见。当然，这是另一种选择，当然不能断言这是惯用的方式。

library(data.table)
df1 <- data.frame(A=1, B=2)
df2 <- data.frame(D=3)

list2env(eapply(.GlobalEnv, function(x) {if(is.data.frame(x)) {setDT(x)} else {x}}), .GlobalEnv)

df1[, rn:=.I]
df1
   A B rn
1: 1 2  1

一些时间安排和内存使用情况:

set.seed(0L)
sz <- 1e7
df1 <- data.frame(A=rnorm(sz))
df2 <- data.frame(B=rnorm(sz))
df3 <- copy(df1)
df4 <- copy(df2)

microbenchmark::microbenchmark(unit="ms", times=1L,
    assign_mtd = {
        for (x in ls()) {
            if (is.data.frame(get(x))) {
                assign(x, as.data.table(get(x)))
            }
        }
    },
    eval_sub_mtd = {
        for(x in ls()){
            if (is.data.frame(get(x))) {
                eval(substitute(setDT(x), list(x=as.name(x))))
            }
        }
    },
    eapply_mtd = {
        list2env(eapply(.GlobalEnv, function(x) {
                if (is.data.frame(x)) setDT(x) else x
            }), .GlobalEnv)
    }
)

时间:

Unit: milliseconds
         expr        min         lq       mean     median         uq        max neval
   assign_mtd 115.922802 115.922802 115.922802 115.922802 115.922802 115.922802     1
 eval_sub_mtd   3.293358   3.293358   3.293358   3.293358   3.293358   3.293358     1
   eapply_mtd   1.913802   1.913802   1.913802   1.913802   1.913802   1.913802     1