summary(cars)
##      speed           dist       
##  Min.   : 4.0   Min.   :  2.00  
##  1st Qu.:12.0   1st Qu.: 26.00  
##  Median :15.0   Median : 36.00  
##  Mean   :15.4   Mean   : 42.98  
##  3rd Qu.:19.0   3rd Qu.: 56.00  
##  Max.   :25.0   Max.   :120.00
plot(cars)

# For Loop
for (i in 1:5){
  print(paste("Iteration", i))
}
## [1] "Iteration 1"
## [1] "Iteration 2"
## [1] "Iteration 3"
## [1] "Iteration 4"
## [1] "Iteration 5"
#While Loop
x <- 1
while (x <=5) {
  print(x^2)
  x<- x + 1
}
## [1] 1
## [1] 4
## [1] 9
## [1] 16
## [1] 25
summarize <- function(x){
  m <- mean(x)
  s <- sd(x)
  return(c(mean=m, sd=s))
}

summarize(c(5, 10, 15, 20))
##      mean        sd 
## 12.500000  6.454972

Loops are great tools to use when coding as they can optimize repetitive instructions or keep things running. While loops and for loops are two very useful kinds.

mexp <- function(x){
  b = 0
  for (i in 1:x){
  b = b + i^2
  }
  print(b)
}

mexp(9)
## [1] 285
mexp(1)
## [1] 1
mexp(4)
## [1] 30