将data.table转换为data.frame（即undo setDT） [英] Convert data.table to data.frame (i.e. undo setDT)

问题描述

我有一个20x2的数据帧。我将该数据帧转换为data.table以执行一些操作（删除了对操作和目标的解释，超出了范围）。转换使我避免使用for循环。但是转换会产生一些问题。

I have a 20x2 dataframe. I converted that dataframe to a data.table to perform some operations (deleted the explanation of the operations and goal as out of scope). The conversion allowed me to avoid using a for loop. But the conversion generates some issues down the line.

我需要将df data.table转换回data.frame。我怎样才能做到这一点？

I need to convert the df data.table back into a data.frame. How can I do that?

非常感谢您的帮助。

df <- data.frame(LastPrice = c( 1221, 1220, 1220, 1217, 1216,  1218 , 1216, 1216, 1217, 1220, 1219, 1218, 1220, 1216, 1217, 1218, 1218, 1207, 1206, 1205), KCT = c( 1218, 1218, 1219, 1218, 1221,  1217 , 1217, 1216, 1219, 1216, 1217, 1216, 1219, 1217, 1218, 1217, 1217, 1217, 1219, 1217))

library(data.table)
setDT(df)
df[, check := as.integer(LastPrice > KCT)]
df[, Signal := do.call(pmin, shift(check, 0:2, type="lead"))]

推荐答案

就像 setDT（）通过引用将其输入转换为数据表一样，还有 setDF（）通过引用将其输入转换为数据帧。因此，只需致电

Just like setDT() converts its input to a data table by reference, there is also setDF() which converts its input to a data frame by reference. So just call

setDF(df)

，您将返回没有副本的数据框。

and you are back to a data frame with no copies made.

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