## sorting dataframes
sort!(df1, [:X2, :Y], rev = (true, false))

# 50x4 DataFrame
# | Row | X1      | X2     | X3      | Y       |
# |     | Float64 | String | Float64 | Float64 |
# +-----+----------+--------+---------+---------+
# | 1   | 1.45373 | Medium | 1.00982 | 2.01964 |
# | 2   | 3.11033 | Medium | 1.01574 | 2.03148 |
# | 3   | 2.12326 | Medium | 1.01782 | 2.03563 |
# :
# | 45  | 2.31324 | High   | 1.82011 | 7.28043 |
# :
# | 50  | 2.33929 | High   | 4.11622 | 16.4649 |
