mydata <- data.frame("ID" = c(1, 2, 3, 4, 5),
                     "Height" = c(170, 172, 174, 176, 180),
                     "Weight" = c(60, 62, 64, 66, 70))
mean(mydata$Height)
## [1] 174.4

On average everyone in the sample has 174.4 cm.

summary(mydata[ ,-1])
##      Height          Weight    
##  Min.   :170.0   Min.   :60.0  
##  1st Qu.:172.0   1st Qu.:62.0  
##  Median :174.0   Median :64.0  
##  Mean   :174.4   Mean   :64.4  
##  3rd Qu.:176.0   3rd Qu.:66.0  
##  Max.   :180.0   Max.   :70.0
mydata$Gender <- c("F", "M", "F", "F", "M")
mydata$BMI <- round(mydata$Weight/(mydata$Height/100)^2,1)