The function trapz accepts x axis vector only for axis=-1. Here is my
modification (correction?) to let it accept a vector x for integration along
any axis:
def trapz(y, x=None, dx=1.0, axis=-1):
"""
Integrate y(x) using samples along the given axis and the composite
trapezoidal rule. If x is None, spacing given by dx is assumed. If x
is an array, it must have either the dimensions of y, or a vector of
length matching the dimension of y along the integration axis.
"""
y = asarray(y)
nd = y.ndim
slice1 = [slice(None)]*nd
slice2 = [slice(None)]*nd
slice1[axis] = slice(1,None)
slice2[axis] = slice(None,-1)
if x is None:
d = dx
else:
x = asarray(x)
if x.ndim == 1:
if len(x) != y.shape[axis]:
raise ValueError('x length (%d) does not match y axis %d length
(%d)' % (len(x), axis, y.shape[axis]))
d = diff(x)
return tensordot(d, (y[slice1]+y[slice2])/2.0,(0, axis))
d = diff(x, axis=axis)
return add.reduce(d * (y[slice1]+y[slice2])/2.0,axis)
Nadav.
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