def transform(self, X, y=None) -> numpy.array:
"""
Return the fractional differentiation of `X`.
Parameters
----------
X : array_like, shape (n_samples, n_series)
Time-series to perform fractional differentiation.
Raises ValueError if `n_samples < self.window_`.
y : array_like, optional
Ignored.
Returns
-------
fdiff : ``numpy.array``, shape (n_samples, n_series)
The fractional differentiation of `X`.
"""
check_is_fitted(self, ["d_"])
check_array(X)
prototype = Fracdiff(0.5, window=self.window,
mode=self.mode).fit_transform(X)
out = numpy.empty_like(prototype[:, :0])
for i in range(X.shape[1]):
f = Fracdiff(self.d_[i], window=self.window, mode=self.mode)
d = f.fit_transform(X[:, [i]])[-out.shape[0]:]
out = numpy.concatenate((out, d), 1)
return out
def invert_diff(df_forecast, columns_diff_dict):
df_fc = df_forecast.copy()
columns = columns_diff_dict.keys()
for col in columns:
f = Fracdiff(d=-columns_diff_dict[col][0],
window=columns_diff_dict[col][1])
diff = f.fit_transform(df_forecast[col].values.reshape(-1, 1))
df_fc[col] = pd.Series(diff.squeeze())
return df_fc
def test_mul(order, seed, n_samples, n_series, a):
"""
Test `D(a * X) = a * D(X)`.
"""
np.random.seed(seed)
X = make_X(n_samples, n_series)
D1 = Fracdiff(order).transform(X)
Da = Fracdiff(order).transform(a * X)
assert np.allclose(a * D1, Da, equal_nan=True)
def howto_spx():
spx = fetch_price('^GSPC')
window = 100
fracdiff = Fracdiff(0.5, window=window)
spx_diff = fracdiff.transform(spx.values.reshape(-1, 1))
spxd = pd.Series(spx_diff[:, 0], index=spx.index)
plot_spx(spx[window:], spxd[window:])
def test_tol_memory(d, tol_memory):
fracdiff = Fracdiff(d, window=None, tol_memory=tol_memory)
try:
fracdiff.transform(X)
window = fracdiff.window_
if d > 1:
d -= floor(d)
assert abs(lost_memory(d, window)) < abs(tol_memory)
except RuntimeWarning: # saturation
pass
def test_transform_twice(d, window, n_blanks_1, n_blanks_2, n_terms, n_series):
"""
Test the correctness of coefficients.
"""
X = make_X(window, n_blanks_1, n_blanks_2, n_terms, n_series)
fracdiff = Fracdiff(d, window=window)
Xd1 = fracdiff.transform(X)
Xd2 = fracdiff.transform(X)
assert np.allclose(Xd1, Xd2, equal_nan=True)
def test_add(order, seed, n_samples, n_series):
"""
Test `D(X1 + X2) = D(X1) + D(X2)`.
"""
np.random.seed(seed)
X1 = make_X(n_samples, n_series)
X2 = make_X(n_samples, n_series)
D1 = Fracdiff(order).transform(X1)
D2 = Fracdiff(order).transform(X2)
DA = Fracdiff(order).transform(X1 + X2)
assert np.allclose(D1 + D2, DA, equal_nan=True)
def test_tol_coef(d, tol_coef):
fracdiff = Fracdiff(d, window=None, tol_coef=tol_coef)
try:
fracdiff.transform(X)
window = fracdiff.window_
if d.is_integer():
assert window == d + 1
else:
if d > 1:
d -= floor(d)
assert abs(last_coef(d, window)) < abs(tol_coef)
except RuntimeWarning: # saturation
pass
def test_coef(d, window, n_blanks_1, n_blanks_2, n_terms, n_series):
"""
Test the correctness of coefficients.
"""
X = make_X(window, n_blanks_1, n_blanks_2, n_terms, n_series)
fracdiff = Fracdiff(d, window=window)
Xd = fracdiff.transform(X)
coef_expected = fracdiff.coef_
for i in range(n_series):
coef = Xd[window + n_blanks_1:, i][:n_terms]
assert np.allclose(coef, coef_expected)
def test_order(self, window, mode, precision):
np.random.seed(42)
X = np.random.randn(1000, 10).cumsum(0)
fs = FracdiffStat(mode=mode, window=window, precision=precision)
fs.fit(X)
X_st = fs.transform(X)
X_ns = np.empty_like(X_st[:, :0])
for i in range(X.shape[1]):
f = Fracdiff(fs.d_[i] - precision, mode=mode, window=window)
X_ns = np.concatenate((X_ns, f.fit_transform(X[:, [i]])), 1)
for i in range(X.shape[1]):
assert self._is_stat(X_st[:, i])
assert not self._is_stat(X_ns[:, i])
def test_transform(self, window, mode, precision):
"""
Test if `FracdiffStat.transform` works
for array with n_features > 1.
"""
np.random.seed(42)
X = np.random.randn(100, 10).cumsum(0)
fs = FracdiffStat(window=window, mode=mode, precision=precision).fit(X)
out = fs.transform(X)
exp = np.empty_like(out[:, :0])
for i in range(X.shape[1]):
f = Fracdiff(fs.d_[i], mode=mode, window=window)
exp = np.concatenate((exp, f.fit_transform(X[:, [i]])), 1)
assert_allclose(out, exp)
def test_sample_pipeline(self, seed, n_samples, n_features, d):
np.random.seed(seed)
X = np.random.randn(n_samples, n_features)
y = np.random.randn(n_samples)
pipeline = Pipeline([
("scaler", StandardScaler()),
("fracdiff", Fracdiff(d)),
("regressor", LinearRegression()),
])
pipeline.fit(X, y)
def test_transform(seed, n_samples, n_features, window):
"""
Test if `StationaryFracdiff.transform` works
for array with n_features > 1.
"""
X = make_nonstationary(seed, n_samples, n_features)
statfracdiff = StationaryFracdiff(window=window).fit(X)
order = statfracdiff.order_
Xd = statfracdiff.transform(X)[window:, :]
Xd_expected = np.concatenate([
Fracdiff(order[i], window).transform(X[:, [i]])[window:, :]
for i in range(n_features)
],
axis=1)
assert np.allclose(Xd, Xd_expected, equal_nan=True)
def test_change_d(d, window, n_blanks_1, n_blanks_2, n_terms, n_series):
"""
Test the correctness of coefficients.
"""
X = make_X(window, n_blanks_1, n_blanks_2, n_terms, n_series)
fracdiff = Fracdiff(0.42, window=window)
_ = fracdiff.transform(X)
fracdiff.d = d
Xd = fracdiff.transform(X)
Xd_expected = Fracdiff(d, window=window).transform(X)
assert np.allclose(Xd, Xd_expected, equal_nan=True)
def test_order(seed, n_samples, n_features, window, precision):
"""
Test if `StationaryFracdiff.order_` is the lowest order to make the
differentiation stationary for array with `n_features > 1`.
"""
X = make_nonstationary(seed, n_samples, n_features)
statfracdiff = StationaryFracdiff(window=window, precision=precision)
statfracdiff.fit(X)
order = statfracdiff.order_
Xd_stat = statfracdiff.transform(X)[window:, :]
Xd_nonstat = np.concatenate([
Fracdiff(order[i] - precision, window).transform(X[:, [i]])[window:, :]
for i in range(n_features)
],
axis=1)
for i in range(n_features):
assert is_stat(Xd_stat[:, i])
assert not is_stat(Xd_nonstat[:, i])
def test_small_n_samples():
fracdiff = Fracdiff(window=100)
with pytest.raises(ValueError):
fracdiff.transform(np.zeros((10, 2)))
def test_saturation():
small_tolerance = 2**(-20)
fracdiff = Fracdiff(0.5, window=None, tol_memory=small_tolerance)
with pytest.raises(RuntimeWarning):
fracdiff.transform(X)
def test_fracdiff_tol_coef(tol_coef):
with pytest.raises(ValueError):
fracdiff = Fracdiff(tol_coef=tol_coef)
fracdiff.transform(X)
def test_fracdiff_tol_memory(tol_memory):
with pytest.raises(ValueError):
fracdiff = Fracdiff(tol_memory=tol_memory)
fracdiff.transform(X)
def test_fracdiff_noparams():
with pytest.raises(ValueError):
fracdiff = Fracdiff(window=None, tol_coef=None, tol_memory=None)
fracdiff.transform(X)
def test_fracdiff_window(window):
with pytest.raises(ValueError):
Fracdiff(window=window).transform(X)
def diff(d):
fracdiff = Fracdiff(d, window=self.window, mode=self.mode)
return fracdiff.fit_transform(x.reshape(-1, 1)).reshape(-1)
def test_transform(self, d, window, mode):
np.random.seed(42)
X = np.random.randn(100, 200)
fracdiff = Fracdiff(d=d, window=window, mode=mode)
out = fdiff(X, n=d, axis=0, window=window, mode=mode)
assert_array_equal(fracdiff.fit_transform(X), out)
def test_repr(self):
fracdiff = Fracdiff(0.5, window=10, mode="full", window_policy="fixed")
expected = "Fracdiff(d=0.5, window=10, mode=full, window_policy=fixed)"
assert repr(fracdiff) == expected
def test_sample_fit_transform(self, seed, n_samples, n_features, d):
np.random.seed(seed)
X = np.random.randn(n_samples, n_features)
_ = Fracdiff(d).fit_transform(X)
def last_coef(d, window):
return Fracdiff(d, window=window)._fit().coef_[-1]
def lost_memory(d, window):
coef = Fracdiff(d, window=LARGE_NUMBER)._fit().coef_
return np.sum(coef[window + 1:])
def test_fracdiff_d(d):
with pytest.raises(ValueError):
Fracdiff(d).transform(X)
import seaborn
sys.path.append("../..")
from fracdiff import Fracdiff # noqa: E402
def fetch_spx():
return pandas_datareader.data.DataReader(
"^GSPC", "yahoo", "1999-10-01", "2020-09-30"
)["Adj Close"]
if __name__ == "__main__":
s = fetch_spx()
f = Fracdiff(0.5, window=100, mode="valid")
d = f.fit_transform(s.values.reshape(-1, 1)).reshape(-1)
s = s[100 - 1 :]
d = pd.Series(d, index=s.index)
seaborn.set_style("white")
fig, ax_s = plt.subplots(figsize=(16, 8))
ax_d = ax_s.twinx()
plot_s = ax_s.plot(s, color="blue", linewidth=0.6, label="S&P 500 (left)")
plot_d = ax_d.plot(
d,
color="orange",
linewidth=0.6,
label="S&P 500, 0.5th differentiation (right)",
)
def test_coef(d, window, n_terms):
coef = Fracdiff(d, window=window)._fit().coef_
coef_expected = get_coefs(d, n_terms)
assert np.allclose(coef, coef_expected)
