Let's take a look at the following two parts:

• The repetition part: Let's take a look at the following steps to get a clear picture of the repetition part:
  1. Let’s first rewrite the fDescriptive function as follows:

             fDescriptive <- function(numVec, type = "classical"){
               avg <- mean(numVec)
               std <- sd(numVec)
               med <- median(numVec)
               medad <- mad(numVec)
               out1 <- c(mean = avg, sd = std)
               out2 <-c(median = med, mad = medad)
               if(type== "classical")
                 return(out1)
               else if (type == "robust")
                 return(out2)
             }

2. Now, using the function, you will calculate robust descriptive statistics for four columns of the iris dataset, a default dataset of flowers in R. This dataset has four numeric variables and one categorical variable:

             robustSummary <- apply(X = iris[,-5], MARGIN = 2, FUN =    
             fDescriptive, type = "robust")

• The recursion part: Let's take a look at the following steps to get a clear picture of the recursion part:
  1. The objective is to write a function to calculate the sum of a cubic series such as 1^3 + 2^3 + … +n^3 using the recursion technique. Let’s give the function name as cubicSum; you will use the cubicSum function within the body of this function as follows:

               cubicSum <- function(n){
                 if(n==0)
                   return(0)
                 else
                   return(n^3 + cubicSum(n-1))
              }

2. The use of the function is as follows:

               cubicSum(n = 3)