def validate(self,
equal_slopes_tolerance=1e-6):
"""
Validate this piecewise linear function by verifying
various properties of the breakpoints and values
lists (e.g., that the list of breakpoints is
nondecreasing).
Args:
equal_slopes_tolerance (float): Tolerance used
check if consecutive slopes are nearly
equal. If any are found, validation will
fail. Default is 1e-6.
Returns:
int:
a function characterization code (see \
:func:`util.characterize_function`)
Raises:
PiecewiseValidationError: if validation fails
"""
breakpoints = [_value(x) for x in self._breakpoints]
values = [_value(x) for x in self._values]
if not is_nondecreasing(breakpoints):
raise PiecewiseValidationError(
"The list of breakpoints is not nondecreasing: %s"
% (str(breakpoints)))
ftype, slopes = characterize_function(breakpoints, values)
for i in range(1, len(slopes)):
if (slopes[i-1] is not None) and \
(slopes[i] is not None) and \
(abs(slopes[i-1] - slopes[i]) <= equal_slopes_tolerance):
raise PiecewiseValidationError(
"Piecewise function validation detected slopes "
"of consecutive line segments to be within %s "
"of one another. This may cause numerical issues. "
"To avoid this error, set the 'equal_slopes_tolerance' "
"keyword to a smaller value or disable validation."
% (equal_slopes_tolerance))
return ftype
def test_is_nondecreasing(self):
self.assertEqual(util.is_nondecreasing([]), True)
self.assertEqual(util.is_nondecreasing([1]), True)
self.assertEqual(util.is_nondecreasing([1, 2]), True)
self.assertEqual(util.is_nondecreasing([1, 2, 3]), True)
self.assertEqual(util.is_nondecreasing([1, 1, 3, 4]), True)
self.assertEqual(util.is_nondecreasing([1, 1, 3, 3]), True)
self.assertEqual(util.is_nondecreasing([1, 1, 1, 4]), True)
self.assertEqual(util.is_nondecreasing([1, 1, 1, 1]), True)
self.assertEqual(util.is_nondecreasing([-1, 1, 1, 1]), True)
self.assertEqual(util.is_nondecreasing([1, -1, 1, 1]), False)
self.assertEqual(util.is_nondecreasing([1, 1, -1, 1]), False)
self.assertEqual(util.is_nondecreasing([1, 1, 1, -1]), False)