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这是我不理解的东西data.table 如果我选择一行,我尝试将此行的所有值设置NA为新行 - data.table被转换为逻辑

#Here is a sample table
DT <- data.table(a=rep(1L,3),b=rep(1.1,3),d=rep('aa',3))
DT
   a   b  d
1: 1 1.1 aa
2: 1 1.1 aa
3: 1 1.1 aa

#Here I extract a line, all the column types are kept... good
str(DT[1])
Classes ‘data.table’ and 'data.frame':  1 obs. of  3 variables:
 $ a: int 1
 $ b: num 1.1
 $ d: chr "aa"
 - attr(*, ".internal.selfref")=<externalptr> 

#Now here I want to set them all to NA...they all become …