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How to find the number of zeros in each column of a data.table object in R?
To find the number of zeros in each column of a data.table object in R, we can follow the below steps −
First of all, create a data.table object.
Then, use colSums function to find the number of zeros in each column.
Example 1
Create the data.table object
Let’s create a data.table as shown below −
library(data.table) x1<-sample(0:2,25,replace=TRUE) x2<-sample(0:2,25,replace=TRUE) x3<-sample(0:2,25,replace=TRUE) DT1<-data.table(x1,x2,x3) DT1
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
x1 x2 x3 1: 0 0 1 2: 1 2 1 3: 2 1 0 4: 1 0 0 5: 2 2 2 6: 1 1 2 7: 0 1 2 8: 2 1 1 9: 1 1 1 10: 0 1 2 11: 1 0 2 12: 1 1 1 13: 1 1 0 14: 2 2 1 15: 2 0 0 16: 2 0 1 17: 0 1 1 18: 2 2 1 19: 1 2 2 20: 2 1 0 21: 1 2 0 22: 1 2 1 23: 2 1 2 24: 2 1 0 25: 0 0 1 x1 x2 x3
Find the number of zeros
Using colSums function to find the number of zeros in each column of data.table object DT1 −
library(data.table) x1<-sample(0:2,25,replace=TRUE) x2<-sample(0:2,25,replace=TRUE) x3<-sample(0:2,25,replace=TRUE) DT1<-data.table(x1,x2,x3) colSums(DT1==0)
Output
x1 x2 x3 5 6 7
Example 2
Create the data.table object
Let’s create a data.table as shown below −
library(data.table) y1<-round(rnorm(25),0) y2<-round(rnorm(25),0) y3<-round(rnorm(25),0) DT2<-data.table(y1,y2,y3) DT2
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
y1 y2 y3 1: 0 -1 0 2: 0 -1 1 3: -2 -1 3 4: -1 -2 0 5: -2 0 1 6: 1 1 -1 7: -1 0 1 8: 0 0 2 9: 1 0 1 10: 0 -1 0 11: -1 -1 1 12: 0 1 0 13: 0 1 0 14: 1 1 0 15: -1 1 1 16: 0 -1 -1 17: 1 0 0 18: 1 2 0 19: -2 1 1 20: -1 1 0 21: -1 1 -3 22: 1 0 1 23: 1 1 0 24: 0 0 1 25: 1 1 -1 y1 y2 y3
Find the number of zeros
Using colSums function to find the number of zeros in each column of data.table object DT2 −
library(data.table) y1<-round(rnorm(25),0) y2<-round(rnorm(25),0) y3<-round(rnorm(25),0) DT2<-data.table(y1,y2,y3) colSums(DT2==0)
Output
y1 y2 y3 8 7 10
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