# R - Functions

I am writing this post who want to learn functions in R. I have solved few examples below. I have provided code also which will be helpful to understand few concepts in R.

Functions in any language basically used to achieve code re-usability. When one has to do repeat particular calculations or task multiple times ,then one can use functions. Function in R take any number of arguments and return the output after processing it.

{

result = a+b

return(result)

}

Please check the following example for more details. I tried to select examples in such a way that all the important building block from R will be touched e.g. loops, conditional statements, sequences, vectors, data-frames, etc.

1. Create a function in R to compute the compound interest.

calCompoundInterest <- function(n,p,r) { A<-p*(1+r/100)^n A[length(n)] - p } n<-1:5 p<-10000 r<-5 calCompoundInterest(n,p,r)

2. Calculate the factorial of a number by creating a function ‘calFactorial’.

calFactorial<-function(n) { total<-1 for(i in 1:n) { total<-total*i } total } calFactorial(5)

3. Write a function which takes vector as an input and calculate the Sharpe Ratio. 𝑆ℎ𝑎𝑟𝑝𝑒 𝑅𝑎𝑡𝑖𝑜= 𝑀𝑒𝑎𝑛 /𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝐷𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛∗√252 (Use the vector: -171.47, 37.24, 265.20, -393.14, 54.65, -183.08, 116.95, 214.19, 356.28, 300.74, 144.74, -270.43, 243.06, 188.60, 373.49)

cal_details<-function(vec) { sharp.ratio<-(mean(vec)/sd(vec) )* sqrt(252) sharp.ratio } cal_details(c(-171.47, 37.24, 265.20, -393.14, 54.65, -183.08, 116.95, 214.19, 356.28, 300.74, 144.74, -270.43, 243.06, 188.60, 373.49))

4. Create a function which calculates the sum for any value n and find f(4).

fun_add_nos<-function(n) { total <-0 for(i in 1:n) total<- total + i return(total) } fun_add_nos(5)

5. Write a function which takes coefficients of quadratic equation as arguments and calculates the roots of the equation.

fun.findroots<-function(c_q_e) { a<-c_q_e b<-c_q_e c<-c_q_e if(b*b < 4*a*c) { root1<-as.complex((-b + (sqrt(b*b-4*a*c)))/2*a) root2<-as.complex((-b - (sqrt(b*b-4*a*c)))/2*a) }else { root1<-(-b + (sqrt(b*b-4*a*c)))/2*a root2<-(-b - (sqrt(b*b-4*a*c)))/2*a } vec<-c(root1,root2) return(vec) } fun.findroots(sample(-40:20,3))