Sorting

Sorting is a fundamental component of data analysis. Basic sorting is trivial: just calling sort! will sort all columns, in place:

usingDataFrames,RDatasetsiris=dataset("datasets","iris")sort!(iris)

In Sorting DataFrames, 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 DataFrame in reverse), and by (to apply a function to a column/DataFrame). 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))