diff options
| -rw-r--r-- | doc/release/upcoming_changes/17577.compatibility.rst | 6 | ||||
| -rw-r--r-- | numpy/lib/polynomial.py | 8 | ||||
| -rw-r--r-- | numpy/lib/tests/test_polynomial.py | 14 |
3 files changed, 24 insertions, 4 deletions
diff --git a/doc/release/upcoming_changes/17577.compatibility.rst b/doc/release/upcoming_changes/17577.compatibility.rst new file mode 100644 index 000000000..d08805607 --- /dev/null +++ b/doc/release/upcoming_changes/17577.compatibility.rst @@ -0,0 +1,6 @@ +poly1d respects the dtype of all-zero argument +---------------------------------------------- +Previously, constructing an instance of ``poly1d`` with all-zero +coefficients would cast the coefficients to ``np.float64``. +This affected the output dtype of methods which construct +``poly1d`` instances internally, such as ``np.polymul``.
\ No newline at end of file diff --git a/numpy/lib/polynomial.py b/numpy/lib/polynomial.py index 7b89eeb70..0fd9bbd79 100644 --- a/numpy/lib/polynomial.py +++ b/numpy/lib/polynomial.py @@ -426,7 +426,7 @@ def polyder(p, m=1): >>> np.polyder(p, 3) poly1d([6]) >>> np.polyder(p, 4) - poly1d([0.]) + poly1d([0]) """ m = int(m) @@ -754,11 +754,11 @@ def polyval(p, x): >>> np.polyval([3,0,1], 5) # 3 * 5**2 + 0 * 5**1 + 1 76 >>> np.polyval([3,0,1], np.poly1d(5)) - poly1d([76.]) + poly1d([76]) >>> np.polyval(np.poly1d([3,0,1]), 5) 76 >>> np.polyval(np.poly1d([3,0,1]), np.poly1d(5)) - poly1d([76.]) + poly1d([76]) """ p = NX.asarray(p) @@ -1236,7 +1236,7 @@ class poly1d: raise ValueError("Polynomial must be 1d only.") c_or_r = trim_zeros(c_or_r, trim='f') if len(c_or_r) == 0: - c_or_r = NX.array([0.]) + c_or_r = NX.array([0], dtype=c_or_r.dtype) self._coeffs = c_or_r if variable is None: variable = 'x' diff --git a/numpy/lib/tests/test_polynomial.py b/numpy/lib/tests/test_polynomial.py index ab6691b43..6c3e4fa02 100644 --- a/numpy/lib/tests/test_polynomial.py +++ b/numpy/lib/tests/test_polynomial.py @@ -227,6 +227,20 @@ class TestPolynomial: v = np.arange(1, 21) assert_almost_equal(np.poly(v), np.poly(np.diag(v))) + def test_zero_poly_dtype(self): + """ + Regression test for gh-16354. + """ + z = np.array([0, 0, 0]) + p = np.poly1d(z.astype(np.int64)) + assert_equal(p.coeffs.dtype, np.int64) + + p = np.poly1d(z.astype(np.float32)) + assert_equal(p.coeffs.dtype, np.float32) + + p = np.poly1d(z.astype(np.complex64)) + assert_equal(p.coeffs.dtype, np.complex64) + def test_poly_eq(self): p = np.poly1d([1, 2, 3]) p2 = np.poly1d([1, 2, 4]) |