1. Create numeric vector that runs from 1 to 10 and let R print it. To create and print it right away, you need to enclose your statement with .
(my_numeric_vector <-seq(1, 10))
#  [1]  1  2  3  4  5  6  7  8  9 10
  1. Now transform that vector so that it's 8th element is being multiplied by 4 and add 7 to it's second element. To access single elements of a vector, you need to use its index via .
my_numeric_vector[c(8, 2)] <- c(my_numeric_vector[8] * 4, 
                                my_numeric_vector[2] + 7)

my_numeric_vector
#  [1]  1  9  3  4  5  6  7 32  9 10
  1. Recode the continent variable into your language, or back to English. To do that, we use the function from the forcats package.
# Recode conti to French.
# Watch out: first the new, then the old value...
conti <- fct_recode(conti, 
                    "Europe" = "Europa", 
                    "Afrique" = "Afrika", 
                    "Asie" = "Asien", 
                    "Amérique Sud" = "Suedamerika") 

table(conti)
# conti
#   Afrique      Asie    Europe S.America 
#         2         1         1         1
  1. Add Atlantis as another level. Now we need the function.
conti <- fct_expand(conti, "Atlantis")

table(conti)
# conti
#   Afrique      Asie    Europe S.America  Atlantis 
#         2         1         1         1         0
  1. Reorder the factor vector such, that Atlantis is shown first. Now we need the function.
conti <- fct_relevel(conti, "Atlantis")

table(conti)
# conti
#  Atlantis   Afrique      Asie    Europe S.America 
#         0         2         1         1         1