Overview of DataFrames - Maple Programming Help

Overview of DataFrames

Description

 • A DataFrame is a two-dimensional data container, similar to a Matrix, but which can contain heterogeneous data, and for which symbolic names may be associated with the rows and columns.

Indexing

 • Each column of a DataFrame is a DataSeries, and the column labels may be used to refer to the corresponding column.
 > df := DataFrame( < 1, 2, 3; 4, 5, 6 >, 'rows' = [ 'a', 'b' ], 'columns' = [ 'A', 'B', 'C' ] );
 ${\mathrm{df}}{≔}\left[\begin{array}{cccc}{}& {A}& {B}& {C}\\ {a}& {1}& {2}& {3}\\ {b}& {4}& {5}& {6}\end{array}\right]$ (1)
 > type( df[ 'B' ], DataSeries );
 ${\mathrm{true}}$ (2)
 • Since each column is a DataSeries, you can index hierarchically into the columns of a DataFrame to extract individual data elements.
 > df[ 'B' ][ 1 ];
 ${2}$ (3)
 > df[ 'B' ][ 'b' ];
 ${5}$ (4)
 • However, you can also select individual data items by specifying the desired row and column indices directly.  (Row and column indices may be either numeric, by position, or symbolic.)
 > df[ 1, 2 ];
 ${2}$ (5)
 > df[ 'a', 'B' ];
 ${2}$ (6)
 • You can use a range or list to select specified columns. In the case of a list, they can come in any desired order.
 > df[ 'A' .. 'B'];
 $\left[\begin{array}{ccc}{}& {A}& {B}\\ {a}& {1}& {2}\\ {b}& {4}& {5}\end{array}\right]$ (7)
 > df[ [ 'B', 'C', 'A' ] ];
 $\left[\begin{array}{cccc}{}& {B}& {C}& {A}\\ {a}& {2}& {3}& {1}\\ {b}& {5}& {6}& {4}\end{array}\right]$ (8)