1. Use ifelse() and your data frame df from exercise IV: If the person is less than or equal to 175 cm, it should have the attribute “small”, otherwise “tall”. Save the result in your df as the new column size.category.
Click here to see the answer 
x <- ifelse(df$size <= 175, "small", "tall")

x
## [1] "small" "small" "tall" "tall" "small"

df$size.categorie <- x

df
##    name age size    city weight size.categorie
## 1  Anna  66  170 Hamburg  115.0          small
## 2  Otto  53  174  Berlin  110.2          small
## 3 Natan  22  182  Berlin   95.0          tall
## 4   Ede  36  180 Cologne   87.0          tall
## 5  Anna  32  174 Hamburg   63.0          small
  1. Write a loop that outputs all integers from 5 to 15!
Click here to see the answer 
vektor <- 5:15
vektor
##  [1]  5  6  7  8  9 10 11 12 13 14 15

for (i in vektor) {
  print(i)
}
## [1] 5
## [1] 6
## [1] 7
## [1] 8
## [1] 9
## [1] 10
## [1] 11
## [1] 12
## [1] 13
## [1] 14
## [1] 15
  1. Advanced: Create a for loop that outputs the arithmetic mean for each variable (column) of your data frame df – provided that the variable is numeric!
Click here to see the answer 
for (i in 1:ncol(df)) {
  
  if (class(df[[i]]) == "numeric") {
    print(names(df)[i])
    result <- mean(df[[i]], na.rm=TRUE)
    print(result)
  }
  
}
## [1] "age"
## [1] 41.8
## [1] "size"
## [1] 176
## [1] "weight"
## [1] 94.04

# Even if it looks complicated, take your time and go through it line by line. Everything should be known by now!