Test

mydata <- data.frame ("ID" = c(1,2,3,4),
                      "AGE"= c(20,22,18,24),
                      "Gender"= c("M","F","M","M"))

print(mydata)

##   ID AGE Gender
## 1  1  20      M
## 2  2  22      F
## 3  3  18      M
## 4  4  24      M

mean(mydata$AGE)

## [1] 21

sd(mydata$AGE)

## [1] 2.581989

The average age of students is 21 years

mydata$Height <- c(180,170,176,177)
mydata$weight <- c(76,60,72,73)

mydata$BMI <- mydata$weight / (mydata$Height/100)*2

Creating new dataframe, which includes only Age and Height (option + š)

mydata2 <- mydata [,c(2,4)]

From my data remove third row

mydata3 <- mydata2[-2,]

Descriptove statistic

summary(mydata[ ,c(-1,-3)])

##       AGE           Height          weight           BMI       
##  Min.   :18.0   Min.   :170.0   Min.   :60.00   Min.   :70.59  
##  1st Qu.:19.5   1st Qu.:174.5   1st Qu.:69.00   1st Qu.:79.01  
##  Median :21.0   Median :176.5   Median :72.50   Median :82.15  
##  Mean   :21.0   Mean   :175.8   Mean   :70.25   Mean   :79.83  
##  3rd Qu.:22.5   3rd Qu.:177.8   3rd Qu.:73.75   3rd Qu.:82.98  
##  Max.   :24.0   Max.   :180.0   Max.   :76.00   Max.   :84.44

#install.packages("pastecs")

library(pastecs)
round(stat.desc(mydata[ , c(-1,-3)]))

##              AGE Height weight BMI
## nbr.val        4      4      4   4
## nbr.null       0      0      0   0
## nbr.na         0      0      0   0
## min           18    170     60  71
## max           24    180     76  84
## range          6     10     16  14
## sum           84    703    281 319
## median        21    176     72  82
## mean          21    176     70  80
## SE.mean        1      2      4   3
## CI.mean.0.95   4      7     11  10
## var            7     18     50  39
## std.dev        3      4      7   6
## coef.var       0      0      0   0

mydata_M <- mydata[mydata$Gender == "M", ]