The near-zero variance, available in the nearZeroVar function in the R package, caret, is used to identify variables that have little or no variance. Consider a set of 10,000 numbers with only three distinct values. Such a variable may add very little value to an algorithm. In order to use the nearZeroVar function, first install the R package, caret, in RStudio (which we had set up Chapter 3, The Analytics Toolkit. The exact code to replicate the effect of using nearZeroVar is shown here:

> library(caret) 
Loading required package: lattice 
Loading required package: ggplot2 
Need help getting started? Try the cookbook for R: http://www.cookbook-r.com/Graphs/ 
 
> repeated <- c(rep(100,9999),10) # 9999 values are 100 and the last value is 10 
 
>random<- sample(100,10000,T) # 10,000 random values from 1 - 100 
 
>data<- data.frame(random = random, repeated = repeated) 
 
>nearZeroVar(data) 
[1] 2 
 
> names(data)[nearZeroVar(data)] 
[1] "repeated" 

As the example shows, the function was able to correctly detect the variable that met the criteria.