从R中的data.table中删除NA [英] Remove rows with NA from data.table in R

问题描述

我想删除任何列中包含 Inf 的 data.table 的所有行。到目前为止，我一直在使用这种方法：

I'd like to remove all rows of a data.table that contain Inf in any of its columns. So far, I've been using this approach:

DT <- data.table(col1 = c(1,2,3), col2 = c(4,Inf,5))
DT[,drop := apply(.SD, 1, function(x) any(is.infinite(x))), by = 1:nrow(DT)]
DT <- DT[(!drop)][,drop:=NULL]

来自这个Stackoverflow问题。然而，这种方法不能很好地扩展到大量的数据。有没有更好的方法来删除 Inf ？

which comes from this Stackoverflow question. However, this approach is not well scalable to large amounts of data. Is there a better way to remove the rows with Inf?

推荐答案

您可以使用 rowSums 来检查行的任何元素是否不是有限的。

You can use rowSums to check if any element of a row is not finite.

DT[is.finite(rowSums(DT))]

或者你可以使用 Inf * 0 是 NA 并使用 complete.cases

OR you can use the fact that Inf * 0 is NA and use complete.cases

DT[complete.cases(DT*0)]

有些基准测试显示 rowSums 对于较小的数据集最快， complete.cases 是较大数据集的最快解决方案。

Some benchmarking shows that the rowSums is fastest for smaller datasets and complete.cases is the fastest solution for larger datasets.

require(microbenchmark)
microbenchmark(
  DT[is.finite(rowSums(DT))]
  ,
  DT[complete.cases(DT*0)]
  ,
  DT[DT[, Reduce('&', lapply(.SD, is.finite))]]
)
##
## nrow(DT) = 3000
## Unit: microseconds                                          
##                                          expr       min       lq      mean    median       uq      max neval cld
##                     DT[is.finite(rowSums(DT))]  786.797  839.235  864.0215  852.8465  884.756 1021.988   100 a  
##                     DT[complete.cases(DT * 0)] 1265.658 1326.575 1363.3985 1350.0055 1386.377 1898.040   100   c
##  DT[DT[, Reduce("&", lapply(.SD, is.finite))]] 1220.137 1275.030 1319.6226 1308.0555 1348.443 1624.023   100  b 
##
## nrow(DT) = 300000
## Unit: milliseconds
##                                           expr       min        lq      mean   median       uq      max neval cld
##                     DT[is.finite(rowSums(DT))] 21.617935 22.687452 26.698070 25.75765 26.07942 87.56290   100   c
##                     DT[complete.cases(DT * 0)]  7.209252  7.567393  9.908503 10.17569 10.37473 71.31375   100 a  
##  DT[DT[, Reduce("&", lapply(.SD, is.finite))]] 11.786773 12.647652 14.128624 14.78512 15.05089 15.39542   100  b 

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