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How to find the index of values in data.table object column in R if they occur once?
To find the index of values in data.table object column in R if they occur once, we can follow the below steps −
First of all, create a data.table object.
Then, use which function along with duplicated function and single square brackets for subsetting to find the index of values in a column if they occur once.
Example 1
Create the data.table object
Let’s create a data.table object as shown below −
library(data.table) x<-sample(1:10,25,replace=TRUE) DT1<-data.table(x) DT1
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
x
1: 3
2: 7
3: 7
4: 2
5: 4
6: 8
7: 10
8: 4
9: 5
10: 9
11: 1
12: 5
13: 8
14: 10
15: 1
16: 10
17: 2
18: 1
19: 10
20: 10
21: 8
22: 2
23: 1
24: 10
25: 4
xFind the index of values in a column if they occur once
Using which function along with duplicated function and single square brackets for subsetting to find the index of values in column x of data.table object DT1 if they occur once −
library(data.table) x<-sample(1:10,25,replace=TRUE) DT1<-data.table(x) which(!(DT1$x %in% DT1$x[duplicated(DT1$x)]))
Output
[1] 1 10
Example 2
Create the data.table object
Let’s create a data.table object as shown below −
library(data.table) y<-rpois(25,10) DT2<-data.table(y) DT2
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
y
1: 9
2: 14
3: 7
4: 5
5: 11
6: 13
7: 8
8: 11
9: 9
10: 10
11: 6
12: 11
13: 10
14: 10
15: 14
16: 13
17: 13
18: 15
19: 9
20: 17
21: 11
22: 17
23: 20
24: 7
25: 12
yFind the index of values in a column if they occur once
Using which function along with duplicated function and single square brackets for subsetting to find the index of values in column y of data.table object DT2 if they occur once−
library(data.table) y<-rpois(25,10) DT2<-data.table(y) which(!(DT2$y %in% DT2$y[duplicated(DT2$y)]))
Output
[1] 4 7 11 18 23 25
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