Variance of a column in R can be calculated by using var() function. var() Function takes column name as argument and calculates the variance of that column. Variance of single column in R, Variance of multiple columns in R using dplyr. Get row wise Variance in R. Let’s see how to calculate Variance in R with an example
- Variance of the single column in R – var() function
- Variance of multiple columns in R
- Variance of Multiple columns in R using dplyr
- Find Variance of the column by column name
- Find Variance of the column by column position
- Get Row wise Variance in R
Let’s first create the dataframe.
### Create Data Frame
df1 = data.frame(Name = c('George','Andrea', 'Micheal','Maggie','Ravi','Xien','Jalpa'),
Grade_score=c(4,6,2,9,5,7,8),
Mathematics1_score=c(45,78,44,89,66,49,72),
Science_score=c(56,52,45,88,33,90,47))
df1
So the resultant dataframe will be
Get Variance of the column in R: Variance of the column by column name
Method 1: Get Variance of the column by column name
# Get Variance of the column by column name var(df1$Mathematics1_score)
Result:
Get Variance of the column in R: Variance of the column by column position
Method 2: Get Variance of the column by column position
# Get Variance of the column by column position var(df1[,3])
Result:
Get Variance of multiple columns R using colVars() : Method 1
ColVars() Function along with sapply() is used to get variance of the multiple column. Dataframe is passed as an argument to ColVars() Function. Variance of numeric columns of the dataframe is calculated.
# Get Variance of the multiple columns colVars(as.matrix(df1[sapply(df1, is.numeric)]))
Variance of numeric columns of the dataframe will be
Get Variance of multiple columns in R using Dplyr : Method 2
summarise_if() Function along with var() function is used to get the variance of the multiple column . With the help of summarise_if() Function, variance of numeric columns of the dataframe is calculated.
# Get Variance of the multiple columns using dplyr library(dplyr) df1 %>% summarise_if(is.numeric, var)
Variance of numeric columns of the dataframe will be
Get Row wise variance in R:
Let’s calculate the row wise variance of mathematics1_score and science_score as shown below using rowVars() function which takes matrix as input. so the dataframe is converted to matrix using as.matrix() function.
# Get Row wise variance in R df1$VAR_score = rowVars(as.matrix(df1[,c(3,4)])) df1
so the resultant dataframe with row wise variance calculated will be
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