scikit-learn/sklearn/preprocessing/tests/test_function_transformer.py

from nose.tools import assert_equal
import numpy as np

from sklearn.utils import testing
from sklearn.preprocessing import FunctionTransformer


def _make_func(args_store, kwargs_store, func=lambda X, *a, **k: X):
    def _func(X, *args, **kwargs):
        args_store.append(X)
        args_store.extend(args)
        kwargs_store.update(kwargs)
        return func(X)

    return _func


def test_delegate_to_func():
    # (args|kwargs)_store will hold the positional and keyword arguments
    # passed to the function inside the FunctionTransformer.
    args_store = []
    kwargs_store = {}
    X = np.arange(10).reshape((5, 2))
    testing.assert_array_equal(
        FunctionTransformer(_make_func(args_store, kwargs_store)).transform(X),
        X,
        'transform should have returned X unchanged',
    )

    # The function should only have received X.
    assert_equal(
        args_store,
        [X],
        'Incorrect positional arguments passed to func: {args}'.format(
            args=args_store,
        ),
    )
    assert_equal(
        kwargs_store,
        {},
        'Unexpected keyword arguments passed to func: {args}'.format(
            args=kwargs_store,
        ),
    )

    # reset the argument stores.
    args_store[:] = []  # python2 compatible inplace list clear.
    kwargs_store.clear()
    y = object()

    testing.assert_array_equal(
        FunctionTransformer(
            _make_func(args_store, kwargs_store),
            pass_y=True,
        ).transform(X, y),
        X,
        'transform should have returned X unchanged',
    )

    # The function should have received X and y.
    assert_equal(
        args_store,
        [X, y],
        'Incorrect positional arguments passed to func: {args}'.format(
            args=args_store,
        ),
    )
    assert_equal(
        kwargs_store,
        {},
        'Unexpected keyword arguments passed to func: {args}'.format(
            args=kwargs_store,
        ),
    )


def test_np_log():
    X = np.arange(10).reshape((5, 2))

    # Test that the numpy.log example still works.
    testing.assert_array_equal(
        FunctionTransformer(np.log1p).transform(X),
        np.log1p(X),
    )


def test_kw_arg():
    X = np.linspace(0, 1, num=10).reshape((5, 2))

    F = FunctionTransformer(np.around, kw_args=dict(decimals=3))

    # Test that rounding is correct
    testing.assert_array_equal(F.transform(X),
                                  np.around(X, decimals=3))


def test_kw_arg_update():
    X = np.linspace(0, 1, num=10).reshape((5, 2))

    F = FunctionTransformer(np.around, kw_args=dict(decimals=3))

    F.kw_args['decimals'] = 1

    # Test that rounding is correct
    testing.assert_array_equal(F.transform(X),
                                  np.around(X, decimals=1))


def test_kw_arg_reset():
    X = np.linspace(0, 1, num=10).reshape((5, 2))

    F = FunctionTransformer(np.around, kw_args=dict(decimals=3))

    F.kw_args = dict(decimals=1)

    # Test that rounding is correct
    testing.assert_array_equal(F.transform(X),
                               np.around(X, decimals=1))


def test_inverse_transform():
    X = np.array([1, 4, 9, 16]).reshape((2, 2))

    # Test that inverse_transform works correctly
    F = FunctionTransformer(
            func=np.sqrt,
            inverse_func=np.around, inv_kw_args=dict(decimals=3))
    testing.assert_array_equal(
            F.inverse_transform(F.transform(X)),
            np.around(np.sqrt(X), decimals=3))