我正在尝试使许多 lm 模型在一个函数中工作,我需要从data.table中自动删除常量列。因此,我只想保留具有两个或多个唯一值的列,但从计数中排除 NA 。
I am trying to get many lm models work in a function and I need to automatically drop constant columns from my data.table. Thus, I want to keep only columns with two or more unique values, excluding NA from the count.
I尝试了在SO上找到的几种方法,但是我仍然无法删除具有两个值的列:常数和NA。
I tried several methods found on SO, but I am still not able to drop columns that have two values: a constant and NAs.
我的可复制代码:
library(data.table) df <- data.table(x=c(1,2,3,NA,5), y=c(1,1,NA,NA,NA),z=c(NA,NA,NA,NA,NA), d=c(2,2,2,2,2)) > df x y z d 1: 1 1 NA 2 2: 2 1 NA 2 3: 3 NA NA 2 4: NA NA NA 2 5: 5 NA NA 2我的意图是删除列y,z和d,因为它们是恒定的,包括y,当省略 NA s时只有一个唯一值。
My intention is to drop columns y, z, and d since they are constant, including y that only have one unique value when NAs are omitted.
我尝试过:
same <- sapply(df, function(.col){ all(is.na(.col)) || all(.col[1L] == .col)}) df1 <- df[ , !same, with = FALSE] > df1 x y 1: 1 1 2: 2 1 3: 3 NA 4: NA NA 5: 5 NA如图所示, y仍然存在... 有帮助吗?
As seen, 'y' is still there ... Any help?
推荐答案由于您有 data.table ,因此可以使用 uniqueN 及其 na.rm 参数:
Because you have a data.table, you may use uniqueN and its na.rm argument:
df[ , lapply(.SD, function(v) if(uniqueN(v, na.rm = TRUE) > 1) v)] # x # 1: 1 # 2: 2 # 3: 3 # 4: NA # 5: 5
一个 base 替代可能是 Filter(function(x)length(unique (x [!is.na(x)]))> 1,df)
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删除带有或不带有NA的常量列
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