[SciPy-User] Double integration with integrate.trapz

[bhanukiran perabathini]

Hi again!

let's say we have a siple function that goes like

def func(x, y):
    return x + y

now I want to get this value for every point on the x-y plane, here's what I do

x = sp.array([-2, -1, 0, 1, 2])
y = sp.array([-2, -1, 0, 1, 2])

xx = x[:, sp.newaxis]
yy = y[sp.newaxis, :]

>>> func(xx, yy)
>>>
array([[-4, -3, -2, -1,  0],
       [-3, -2, -1,  0,  1],
       [-2, -1,  0,  1,  2],
       [-1,  0,  1,  2,  3],
       [ 0,  1,  2,  3,  4]])

works as expected right?

How do we get the following function working with broadcasted arrays?

def func2(x, y):
    if x > y:
       return x + y
    else:
       return x - y

func2(xx, yy) raises the error
ValueError: The truth value of an array with more than one element is
ambiguous. Use a.any() or a.all()


How do we handle such situations?


Thanks so much,
Bhanukiran


On Mon, Feb 28, 2011 at 2:48 PM, bhanukiran perabathini
<bhanukiran.perabathini at gmail.com> wrote:
> oh looks like this is what i've been looking for..
>
> http://www.scipy.org/EricsBroadcastingDoc
>
>
>
> On Mon, Feb 28, 2011 at 12:08 PM, bhanukiran perabathini
> <bhanukiran.perabathini at gmail.com> wrote:
>> Hi Pauli Virtanen & Giacomo Boffi,
>>
>> Both of your suggestions helped me. thanks so much.
>>
>> But I guess I'm having some troubles understanding and using
>> broadcasting to its total power. Could you suggest some tutorial where
>> I can read up learn this stuff?
>>
>> Manipulating with the axes seems a little tricky to me. I want to
>> master them so well that I can think in terms of them.
>>
>> Thanks again for your time,
>> Bhanukiran
>>
>>
>>
>> On Sun, Feb 27, 2011 at 5:04 PM, Giacomo Boffi <giacomo.boffi at polimi.it> wrote:
>>> bhanukiran perabathini writes:
>>>
>>>  > - My task is to perform a double integral (with two free variables)
>>>  >   and make a filled-contour plot of the logarithm of its absolute
>>>  >   square.
>>>
>>> notwistanding the other excellent advice you've received, please note
>>> that your integral is symmetric with respect to the free variables, so
>>> that you could double the resolution of your plot using the same
>>> amount of computational resources plotting the first quadrant only
>>>
>>> --
>>> anch'io la penso come me, ma                     -- SteO153, in IHC
>>>
>>> --
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>>
>