Have you thought about using cython to work with the numpy C-API ( http://wiki.cython.org/tutorials/numpy#UsingtheNumpyCAPI)? This will be fast, simple (you can mix and match Python and Cython).
As for your specific issue: you can simply cast to all the inputs to numpy arrays (using asarray http://docs.scipy.org/doc/numpy/reference/generated/numpy.asarray.html) to deal with scalars. This will make sure they get broadcast correctly. On Tue, Feb 1, 2011 at 11:22 AM, <dpar...@chromalloy.com> wrote: > Thanks for the advice. > > Using Sebastian's advice I was able to write a version that worked when the > input arguments are both arrays with the same length. The code provided by > eat works when t is an array, but not for an array of far. > > The numpy.vectorize version works with any combination of scalar or array > input. I still haven't figured out how to rewrite my function to be as > flexible as the numpy.vectorize version at accepting either scalars or array > inputs and properly broadcasting the scalar arguments to the array > arguments. > > David Parker > Chromalloy - TDAG > > > > From: eat <e.antero.ta...@gmail.com> > To: Discussion of Numerical Python <numpy-discussion@scipy.org> > Date: 01/31/2011 11:37 AM > Subject: Re: [Numpy-discussion] Vectorize or rewrite function to > work with array inputs? > Sent by: numpy-discussion-boun...@scipy.org > ------------------------------ > > > > Hi, > > On Mon, Jan 31, 2011 at 5:15 PM, > <*dpar...@chromalloy.com*<dpar...@chromalloy.com>> > wrote: > I have several functions like the example below that I would like to make > compatible with array inputs. The problem is the conditional statements give > a *ValueError: The truth value of an array with more than one element is > ambiguous. Use a.any() or a.all()*. I can use numpy.vectorize, but if > possible I'd prefer to rewrite the function. Does anyone have any advice the > best way to modify the code to accept array inputs? Thanks in advance for > any assistance. > > If I understod your question correctly, then air_gamma could be coded as: > def air_gamma_0(t, far=0.0): > """ > Specific heat ratio (gamma) of Air/JP8 > t - static temperature, Rankine > [far] - fuel air ratio [- defaults to 0.0 (dry air)] > air_gamma - specific heat ratio > """ > if far< 0.: > return NAN > elif far < 0.005: > ag= air_gamma_1(t) > ag[np.logical_or(t< 379., t> 4731.)]= NAN > return ag > elif far< 0.069: > ag= air_gamma_2(t, far) > ag[np.logical_or(t< 699., t> 4731.)]= NAN > return ag > else: > return NAN > Rest of the code is in the attachment. > > > My two cents, > eat > > > > NAN = float('nan') > > def air_gamma(t, far=0.0): > """ > Specific heat ratio (gamma) of Air/JP8 > t - static temperature, Rankine > [far] - fuel air ratio [- defaults to 0.0 (dry air)] > air_gamma - specific heat ratio > """ > if far < 0.: > return NAN > elif far < 0.005: > if t < 379. or t > 4731.: > return NAN > else: > air_gamma = -3.472487e-22 * t ** 6. + 6.218811e-18 * t ** 5. - > 4.428098e-14 * t ** 4. + 1.569889e-10 * t ** 3. - 0.0000002753524 * t ** 2. > + 0.0001684666 * t + 1.368652 > elif far < 0.069: > if t < 699. or t > 4731.: > return NAN > else: > a6 = 4.114808e-20 * far ** 3. - 1.644588e-20 * far ** 2. + > 3.103507 <tel:+13103507>e-21 * far - 3.391308e-22 > a5 = -6.819015e-16 * far ** 3. + 2.773945e-16 * far ** 2. - > 5.469399e-17 * far + 6.058125e-18 > a4 = 4.684637e-12 * far ** 3. - 1.887227e-12 * far ** 2. + > 3.865306e-13 * far - 4.302534e-14 > a3 = -0.00000001700602 * far ** 3. + 0.000000006593809 * far ** > 2. - 0.000000001392629 * far + 1.520583e-10 > a2 = 0.00003431136 * far ** 3. - 0.00001248285 * far ** 2. + > 0.000002688007 * far - 0.0000002651616 > a1 = -0.03792449 * far ** 3. + 0.01261025 * far ** 2. - > 0.002676877 * far + 0.0001580424 > a0 = 13.65379 * far ** 3. - 3.311225 * far ** 2. + 0.3573201 * > far + 1.372714 > air_gamma = a6 * t ** 6. + a5 * t ** 5. + a4 * t ** 4. + a3 * t > ** 3. + a2 * t ** 2. + a1 * t + a0 > elif far >= 0.069: > return NAN > else: > return NAN > return air_gamma > > David Parker > Chromalloy - TDAG > _______________________________________________ > NumPy-Discussion mailing list* > **NumPy-Discussion@scipy.org* <NumPy-Discussion@scipy.org>* > **http://mail.scipy.org/mailman/listinfo/numpy-discussion*<http://mail.scipy.org/mailman/listinfo/numpy-discussion> > > [attachment "air_gamma.py" deleted by Dave Parker/Chromalloy] > _______________________________________________ > > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > >
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