mydata <- data.frame("ID" = c(1, 2, 3, 4, 5),
                     "Height" = c(170, 172, 180, 182, 186),
                     "Weight" = c(60, 65, 70, 77, 82))
mean(mydata$Height) #Estimation of the arithmetic mean
## [1] 178

On average everyone in the sample has 178 cm.

summary(mydata[ ,  -1])
##      Height        Weight    
##  Min.   :170   Min.   :60.0  
##  1st Qu.:172   1st Qu.:65.0  
##  Median :180   Median :70.0  
##  Mean   :178   Mean   :70.8  
##  3rd Qu.:182   3rd Qu.:77.0  
##  Max.   :186   Max.   :82.0
mydata$Gender <- c("F", "F", "M", "M", "M")

Calculate a new variable, called BMI.

mydata$BMI <- round(mydata$Weight / (mydata$Height/100)^2, 1)