Sorting
Sorting is a fundamental component of data analysis. Basic sorting is trivial: just calling sort!
will sort all columns, in place:
using DataValueTables
using CSV
iris = CSV.read(joinpath(Pkg.dir("DataValueTables"), "test/data/iris.csv"), DataValueTable)
sort!(iris)
In Sorting DataValueTables, you may want to sort different columns with different options. Here are some examples showing most of the possible options:
sort!(iris, rev = true)
sort!(iris, cols = [:SepalWidth, :SepalLength])
sort!(iris, cols = [order(:Species, by = uppercase),
order(:SepalLength, rev = true)])
Keywords used above include cols
(to specify columns), rev
(to sort a column or the whole DataValueTable in reverse), and by
(to apply a function to a column/DataValueTable). Each keyword can either be a single value, or can be a tuple or array, with values corresponding to individual columns.
As an alternative to using array or tuple values, order
to specify an ordering for a particular column within a set of columns
The following two examples show two ways to sort the iris
dataset with the same result: Species
will be ordered in reverse lexicographic order, and within species, rows will be sorted by increasing sepal length and width:
sort!(iris, cols = (:Species, :SepalLength, :SepalWidth),
rev = (true, false, false))
sort!(iris, cols = (order(:Species, rev = true), :SepalLength, :SepalWidth))