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.
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
2) Write a loop that outputs all integers from 5 to 15!
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
3) 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!
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!