具体删除与R的所有重复 [英] Specific removing all duplicates with R

问题描述

例如，我有两个列：

  Var1 Var2 
 1 12 
 1 65 
 2 68 
 2 98 
 3 49 
 3 24 
 4 8 
 5 67 
 6 12 
  
 
 
 
我需要显示列Var1唯一的值：
  Var1 Var2 
 4 8 
 5 67 
 6 12 
  
 
 b $ b 
我可以这样做：
  mydata = mydata [！unique（mydata $ Var1） 
 
但是当我对大型数据集使用相同的公式，大约100万条观察值时，没有任何反应 - 样本大小仍然相同。 
 
 
 
谢谢！
解决方案
使用 data.table （因为它似乎标记了它）我会做
  indx <-setDT（DT）[，.I [.N == 1]，by = Var1] $ V1 
 DT [indx] 
＃Var1 Var2 
＃ 1：4 8 
＃2：5 67 
＃3：6 12 
  
 or ... as @eddi提醒我，你可以简单地做
  DT [，if（.N == 1） .SD，by = Var1] 
  
或者（根据提及的重复项）与 v> = 1.9.5 您也可以执行
  setDT（DT，key =Var1）[！（duplicate（DT）| duplicated（DT，fromLast = TRUE））] 
  
 
For example I have two columns:
 Var1 Var2
 1     12
 1     65
 2     68
 2     98
 3     49
 3     24
 4      8
 5     67
 6     12
And I need to display only values which are unique for column Var1:
 Var1 Var2
 4      8
 5     67
 6     12
I can do you like this: 
 mydata=mydata[!unique(mydata$Var1),]
But when I use the same formula for my large data set with about 1 million observations, nothing happens - the sample size is still the same.  Could you please explain my why?

Thank you!
解决方案
With data.table (as it seem to be tagged with it) I would do
indx <- setDT(DT)[, .I[.N == 1], by = Var1]$V1 
DT[indx]
#    Var1 Var2
# 1:    4    8
# 2:    5   67
# 3:    6   12
Or... as @eddi reminded me, you can simply do
DT[, if(.N == 1) .SD, by = Var1]
Or (per the mentioned duplicates) with v >= 1.9.5 you could also do something like 
setDT(DT, key = "Var1")[!(duplicated(DT) | duplicated(DT, fromLast = TRUE))]


                        
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