[Numpy-discussion] Vectorize or rewrite function to work with array inputs?

[eat]

Hi,

On Mon, Jan 31, 2011 at 5:15 PM, <DParker at 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
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> NumPy-Discussion at scipy.org
> http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
>
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