2.5. Sorting - JulTob/R GitHub Wiki

In data analysis you can sort your data according to a certain variable in the dataset. In R, this is done with the help of the function order().

a <- c(100, 10, 1000)
order(a)
[1] 2 1 3

10, which is the second element in a, is the smallest element, so 2 comes first in the output of order(a). 100, which is the first element in a is the second smallest element, so 1 comes second in the output of order(a).

This means we can use the output of order(a) to reshuffle a:

a[order(a)]
[1]   10  100 1000

# Use order() to create positions
positions <-  order(planets_df$diameter)
positions

# Use positions to sort planets_df
planets_df[positions, ]

     name               type diameter rotation rings
1 Mercury Terrestrial planet    0.382    58.64 FALSE
4    Mars Terrestrial planet    0.532     1.03 FALSE
2   Venus Terrestrial planet    0.949  -243.02 FALSE
3   Earth Terrestrial planet    1.000     1.00 FALSE
8 Neptune          Gas giant    3.883     0.67  TRUE
7  Uranus          Gas giant    4.007    -0.72  TRUE
6  Saturn          Gas giant    9.449     0.43  TRUE
5 Jupiter          Gas giant   11.209     0.41  TRUE