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> 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. +
3.103507e-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
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
