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How to find the column standard deviation if some columns are categorical in R data frame?
To find the column standard deviation if some columns are categorical in R data frame, we can follow the below steps −
First of all, create a data frame.
Then, use numcolwise function from plyr package to find the column standard deviation if some columns are categorical.
Example 1
Create the data frame
Let’s create a data frame as shown below −
Group<-sample(c("I","II","III","IV"),25,replace=TRUE)
Num1<-sample(1:50,25)
Num2<-sample(1:50,25)
df1<-data.frame(Group,Num1,Num2)
df1Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
Group Num1 Num2 1 IV 30 18 2 III 26 1 3 II 38 6 4 II 37 7 5 II 49 22 6 I 7 47 7 II 34 23 8 III 23 44 9 IV 24 11 10 II 36 28 11 II 31 13 12 IV 27 8 13 I 22 20 14 IV 25 38 15 IV 44 15 16 III 43 5 17 I 21 29 18 III 40 48 19 I 46 41 20 IV 8 36 21 IV 20 27 22 III 16 24 23 II 15 9 24 I 48 30 25 IV 3 39
Find the column standard deviation if some columns are categorical
Using numcolwise function from plyr package to find the column standard deviation of numerical columns in the data frame df1 −
Group<-sample(c("I","II","III","IV"),25,replace=TRUE)
Num1<-sample(1:50,25)
Num2<-sample(1:50,25)
df1<-data.frame(Group,Num1,Num2)
library(plyr)
numcolwise(sd)(df1)Output
Num1 Num2 1 13.57424 14.9295
Example 2
Create the data frame
Let’s create a data frame as shown below −
Categories<-sample(c("First","Second","Third"),25,replace=TRUE)
Score<-sample(1:10,25,replace=TRUE)
Price<-sample(1:5,25,replace=TRUE)
df2<-data.frame(Categories,Score,Price)
df2Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
Categories Score Price 1 Second 10 5 2 Third 5 3 3 Second 10 4 4 Third 2 3 5 Third 1 1 6 First 4 2 7 First 6 3 8 Second 3 4 9 Second 2 4 10 Third 8 3 11 First 8 1 12 Second 8 3 13 First 2 2 14 First 5 1 15 First 10 3 16 Third 7 3 17 Second 4 2 18 Second 7 2 19 Second 2 5 20 First 5 1 21 Third 10 3 22 Second 10 4 23 Third 2 5 24 Third 4 3 25 First 3 4
Find the column standard deviation if some columns are categorical
Using numcolwise function from plyr package to find the column standard deviation of numerical columns in the data frame df2 −
Categories<-sample(c("First","Second","Third"),25,replace=TRUE)
Score<-sample(1:10,25,replace=TRUE)
Price<-sample(1:5,25,replace=TRUE)
df2<-data.frame(Categories,Score,Price)
library(plyr)
numcolwise(sd)(df2)Output
Score Price 1 3.006659 1.670329
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