應用Data.table函數後保持列名相同

Question

我有以下代碼行從數據框「Diff」中提取某些列。當應用data.table函數時，列名將被重命名爲V1，V2，V3等。我如何保持列名與以前相同（因爲它們出現在Diff數據框中）？

data.table(Diff$FactSet.Fund.Code, Diff$FactsetDate.x, , Diff$DeskName.x) 

Answer 1

假設當你從一個data.frame去data.table出現問題，你可以先用diff <- data.table(diff)把你data.frame在其整體的data.table。 然後您可以使用subset()輕鬆地將您的data.table子集以及您想要保留的列名稱列表。這樣你會保留你的原名。這裏所說：

# Libraries 
library(data.frame) 

# Here's dataframe with some random data 
# that fits your description: 
diff = data.frame(FactSet.Fund.Code=rep(c("a","b"),c(2,3)),FactsetDate.x=1:5,FactsetSomethingelse=5:1) 
#class(diff) 

diff = data.table(diff) 
#class(diff) 

# The names fo the columns you'd like to keep: 
selection = c('FactSet.Fund.Code','FactsetDate.x') 

# Your desired subset: 
diff <- subset(diff,,selection) 

# And now it should look like this: 

    FactSet.Fund.Code FactsetDate.x 
1:     a    1 
2:     a    2 
3:     b    3 
4:     b    4 
5:     b    5