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gradient() function now supports datetime64 and timedelta64 #167

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gradient() function now supports datetime64 and timedelta64 #167

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cf1d759
gradient() function now supports datetime64 and timedelta64
WeatherGod Sep 27, 2011
5b9c03e
Added compatibility for timedelta64 to gradient
WeatherGod Jan 22, 2012
2f9f219
Tests for gradient() of datetime64 and timedelta64
WeatherGod Jan 22, 2012
e927d05
Use empty_like() in the gradient function to maintain C/F-order
WeatherGod Jan 25, 2012
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13 changes: 11 additions & 2 deletions numpy/lib/function_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -867,6 +867,7 @@ def gradient(f, *varargs):
[ 1. , 1. , 1. ]])]

"""
f = np.asanyarray(f)
N = len(f.shape) # number of dimensions
n = len(varargs)
if n == 0:
Expand All @@ -889,12 +890,20 @@ def gradient(f, *varargs):
slice3 = [slice(None)]*N

otype = f.dtype.char
if otype not in ['f', 'd', 'F', 'D']:
if otype not in ['f', 'd', 'F', 'D', 'm', 'M']:
otype = 'd'

# Difference of datetime64 elements results in timedelta64
if otype == 'M' :
# Need to use the full dtype name because it contains unit information
otype = f.dtype.name.replace('datetime', 'timedelta')
elif otype == 'm' :
# Needs to keep the specific units, can't be a general unit
otype = f.dtype

for axis in range(N):
# select out appropriate parts for this dimension
out = np.zeros_like(f).astype(otype)
out = np.empty_like(f, dtype=otype)
slice1[axis] = slice(1, -1)
slice2[axis] = slice(2, None)
slice3[axis] = slice(None, -2)
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14 changes: 14 additions & 0 deletions numpy/lib/tests/test_function_base.py
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Expand Up @@ -281,6 +281,20 @@ def test_masked(self):
x = np.ma.array([[1, 1], [3, 4]])
assert_equal(type(gradient(x)[0]), type(x))

def test_datetime64(self):
# Make sure gradient() can handle special types like datetime64
x = array(['1910-08-16', '1910-08-11', '1910-08-10', '1910-08-12',
'1910-10-12', '1910-12-12', '1912-12-12'],
dtype='datetime64[D]')
dx = array([ -5, -3, 0, 31, 61, 396, 731], dtype='timedelta64[D]')
assert_array_equal(gradient(x), dx)

def test_timedelta64(self):
# Make sure gradient() can handle special types like timedelta64
x = array([-5, -3, 10, 12, 61, 321, 300], dtype='timedelta64[D]')
dx = array([ 2, 7, 7, 25, 154, 119, -21], dtype='timedelta64[D]')
assert_array_equal(gradient(x), dx)


class TestAngle(TestCase):
def test_basic(self):
Expand Down