[SciPy-User] Double integration with integrate.trapz

[eat]

Hi

On Mon, Feb 28, 2011 at 1:05 PM, bhanukiran perabathini <
bhanukiran.perabathini at gmail.com> wrote:

> 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?
>
For example
In []: x= arange(5)
In []: y= arange(5)
In []: xx= x[:, None]
In []: yy= y[None, :]
In []: A= xx+ yy
In []: A[xx< yy]= (xx- yy)[xx< yy]
In []: A
Out[]:
array([[ 0, -1, -2, -3, -4],
       [ 1,  2, -1, -2, -3],
       [ 2,  3,  4, -1, -2],
       [ 3,  4,  5,  6, -1],
       [ 4,  5,  6,  7,  8]])

Regards,
eat

>
>
> 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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> >>>
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> >>
> >
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