Question

Here I found an example of using integrate.cumtrapz(), but it doesn’t work for me – when I try to set initial=0 in

y_int = integrate.cumtrapz(y, x, initial=0)

I get an error

TypeError: cumtrapz() got an unexpected keyword argument 'initial'

What’s the problem?

Answer 1

What version of scipy are you running? I’ve scipy 0.10.1, and the keyword initial is not recognized either. Moreover, the docstring does not have it either, while the source code for scipy 0.11 (which you linked) has it. Which leads me to a guess that it’s something which was added in v 0.11.

Indeed:

>>> import scipy.integrate as si
>>> si.__file__
'/usr/local/lib/python2.6/dist-packages/scipy/integrate/__init__.pyc'

then checking the source (which is in quadrature.py) — the signature is

 def cumtrapz(y, x=None, dx=1.0, axis=-1):

To check the scipy version, do this:

>>> scipy.__version__
'0.10.1'