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How to subset a data.table object in R by specifying columns that contains NA?
To subset a data.table object by specifying columns that contains NA, we can follow the below steps −
First of all, create a data.table object with some columns containing NAs.
Then, use is.na along with subset function to subset the data.table object by specifying columns that contains NA.
Example
Create the data.table object
Let’s create a data.table object as shown below −
library(data.table) x1<-sample(c(NA,round(rnorm(2),2)),25,replace=TRUE) x2<-sample(c(NA,round(rnorm(3),2)),25,replace=TRUE) x3<-sample(c(NA,round(rnorm(3),2)),25,replace=TRUE) x4<-sample(c(NA,round(rnorm(2),2)),25,replace=TRUE) DT<-data.table(x1,x2,x3,x4) DT
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
x1 x2 x3 x4
1: -2.34 -0.57 NA NA
2: -2.34 -0.57 -0.85 -0.47
3: NA -0.57 NA -0.47
4: -2.34 -0.57 -0.84 0.69
5: NA -0.57 1.82 0.69
6: 1.14 -2.03 1.82 NA
7: -2.34 NA -0.84 NA
8: 1.14 0.63 -0.85 NA
9: NA NA -0.84 -0.47
10: 1.14 NA NA -0.47
11: -2.34 NA -0.84 NA
12: NA NA -0.85 NA
13: 1.14 0.63 -0.84 NA
14: -2.34 0.63 -0.84 NA
15: -2.34 -2.03 1.82 NA
16: NA -2.03 1.82 NA
17: NA NA NA -0.47
18: 1.14 -2.03 NA NA
19: NA 0.63 1.82 NA
20: -2.34 NA 1.82 -0.47
21: 1.14 0.63 NA NA
22: 1.14 NA -0.85 -0.47
23: -2.34 -2.03 NA -0.47
24: 1.14 0.63 1.82 -0.47
25: -2.34 NA NA 0.69
x1 x2 x3 x4Subset data.table object by specifying columns having NAs
Using is.na along with subset function to subset the data.table object DT by specifying columns x1 and x2 that contains NA as shown below −
library(data.table) x1<-sample(c(NA,round(rnorm(2),2)),25,replace=TRUE) x2<-sample(c(NA,round(rnorm(3),2)),25,replace=TRUE) x3<-sample(c(NA,round(rnorm(3),2)),25,replace=TRUE) x4<-sample(c(NA,round(rnorm(2),2)),25,replace=TRUE) DT<-data.table(x1,x2,x3,x4) subset(DT,is.na(x1)|is.na(x2))
Output
x1 x2 x3 x4 1: NA -0.57 NA -0.47 2: NA -0.57 1.82 0.69 3: -2.34 NA -0.84 NA 4: NA NA -0.84 -0.47 5: 1.14 NA NA -0.47 6: -2.34 NA -0.84 NA 7: NA NA -0.85 NA 8: NA -2.03 1.82 NA 9: NA NA NA -0.47 10: NA 0.63 1.82 NA 11: -2.34 NA 1.82 -0.47 12: 1.14 NA -0.85 -0.47 13: -2.34 NA NA 0.69
Updated on: 15-Nov-2021
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