datascience.tables.Table.where

Table.where(column_or_label, value_or_predicate=None, other=None)[source]

Return a new Table containing rows where value_or_predicate returns True for values in column_or_label.

Args:

column_or_label: A column of the Table either as a label (str) or an index (int). Can also be an array of booleans; only the rows where the array value is True are kept.

value_or_predicate: If a function, it is applied to every value in column_or_label. Only the rows where value_or_predicate returns True are kept. If a single value, only the rows where the values in column_or_label are equal to value_or_predicate are kept.

other: Optional additional column label for value_or_predicate to make pairwise comparisons. See the examples below for usage. When other is supplied, value_or_predicate must be a callable function.

Returns:

If value_or_predicate is a function, returns a new Table containing only the rows where value_or_predicate(val) is True for the val``s in ``column_or_label.

If value_or_predicate is a value, returns a new Table containing only the rows where the values in column_or_label are equal to value_or_predicate.

If column_or_label is an array of booleans, returns a new Table containing only the rows where column_or_label is True.

>>> marbles = Table().with_columns(
...    "Color", make_array("Red", "Green", "Blue",
...                        "Red", "Green", "Green"),
...    "Shape", make_array("Round", "Rectangular", "Rectangular",
...                        "Round", "Rectangular", "Round"),
...    "Amount", make_array(4, 6, 12, 7, 9, 2),
...    "Price", make_array(1.30, 1.20, 2.00, 1.75, 0, 3.00))

>>> marbles
Color | Shape       | Amount | Price
Red   | Round       | 4      | 1.3
Green | Rectangular | 6      | 1.2
Blue  | Rectangular | 12     | 2
Red   | Round       | 7      | 1.75
Green | Rectangular | 9      | 0
Green | Round       | 2      | 3

Use a value to select matching rows

>>> marbles.where("Price", 1.3)
Color | Shape | Amount | Price
Red   | Round | 4      | 1.3

In general, a higher order predicate function such as the functions in datascience.predicates.are can be used.

>>> from datascience.predicates import are
>>> # equivalent to previous example
>>> marbles.where("Price", are.equal_to(1.3))
Color | Shape | Amount | Price
Red   | Round | 4      | 1.3

>>> marbles.where("Price", are.above(1.5))
Color | Shape       | Amount | Price
Blue  | Rectangular | 12     | 2
Red   | Round       | 7      | 1.75
Green | Round       | 2      | 3

Use the optional argument other to apply predicates to compare columns.

>>> marbles.where("Price", are.above, "Amount")
Color | Shape | Amount | Price
Green | Round | 2      | 3

>>> marbles.where("Price", are.equal_to, "Amount") # empty table
Color | Shape | Amount | Price