diff options
Diffstat (limited to 'numpy/lib')
| -rw-r--r-- | numpy/lib/function_base.py | 21 | ||||
| -rw-r--r-- | numpy/lib/tests/test_function_base.py | 11 |
2 files changed, 27 insertions, 5 deletions
diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py index 3533a59fc..24afa39c2 100644 --- a/numpy/lib/function_base.py +++ b/numpy/lib/function_base.py @@ -639,6 +639,9 @@ def histogram(a, bins=10, range=None, normed=False, weights=None, # Pre-compute histogram scaling factor norm = bins / (mx - mn) + # Compute the bin edges for potential correction. + bin_edges = linspace(mn, mx, bins + 1, endpoint=True) + # We iterate over blocks here for two reasons: the first is that for # large arrays, it is actually faster (for example for a 10^8 array it # is 2x as fast) and it results in a memory footprint 3x lower in the @@ -657,14 +660,22 @@ def histogram(a, bins=10, range=None, normed=False, weights=None, tmp_a = tmp_a[keep] if tmp_w is not None: tmp_w = tmp_w[keep] - tmp_a = tmp_a.astype(float) - tmp_a -= mn + tmp_a_data = tmp_a.astype(float) + tmp_a = tmp_a_data - mn tmp_a *= norm # Compute the bin indices, and for values that lie exactly on mx we # need to subtract one indices = tmp_a.astype(np.intp) - indices[indices == bins] -= 1 + equals_endpoint = (indices == bins) + indices[equals_endpoint] -= 1 + + # The index computation is not guaranteed to give exactly + # consistent results within ~1 ULP of the bin edges. + decrement = tmp_a_data < bin_edges[indices] + indices[decrement] -= 1 + increment = (tmp_a_data >= bin_edges[indices + 1]) & ~equals_endpoint + indices[increment] += 1 # We now compute the histogram using bincount if ntype.kind == 'c': @@ -673,8 +684,8 @@ def histogram(a, bins=10, range=None, normed=False, weights=None, else: n += np.bincount(indices, weights=tmp_w, minlength=bins).astype(ntype) - # We now compute the bin edges since these are returned - bins = linspace(mn, mx, bins + 1, endpoint=True) + # Rename the bin edges for return. + bins = bin_edges else: bins = asarray(bins) if (np.diff(bins) < 0).any(): diff --git a/numpy/lib/tests/test_function_base.py b/numpy/lib/tests/test_function_base.py index 0f71393ad..868a28036 100644 --- a/numpy/lib/tests/test_function_base.py +++ b/numpy/lib/tests/test_function_base.py @@ -1407,6 +1407,17 @@ class TestHistogram(TestCase): assert_raises(ValueError, histogram, vals, range=[np.nan,0.75]) assert_raises(ValueError, histogram, vals, range=[0.25,np.inf]) + def test_bin_edge_cases(self): + # Ensure that floating-point computations correctly place edge cases. + arr = np.array([337, 404, 739, 806, 1007, 1811, 2012]) + hist, edges = np.histogram(arr, bins=8296, range=(2, 2280)) + mask = hist > 0 + left_edges = edges[:-1][mask] + right_edges = edges[1:][mask] + for x, left, right in zip(arr, left_edges, right_edges): + self.assertGreaterEqual(x, left) + self.assertLess(x, right) + class TestHistogramOptimBinNums(TestCase): """ |