[SciPy-User] odeint

nicky van foreest vanforeest@gmail....
Thu Aug 16 03:08:05 CDT 2012


Hi Chuck,

Thanks for your suggestion. I already have something working now,
based on the Rob's idea with splines. BTW, I first used interp1d, but
that gave some problems at the boundaries due to tiny rounding errors.
I now use univariatespline as this gives a function that also extends
beyond the boundaries, hence can deal with the rounding problems.

Nicky

On 16 August 2012 03:58, Charles R Harris <charlesr.harris@gmail.com> wrote:
>
>
> On Sun, Aug 12, 2012 at 1:49 PM, nicky van foreest <vanforeest@gmail.com>
> wrote:
>>
>> Hi Rob,
>>
>> Thanks for the suggestion. I didn't think of using splines.
>>
>> Nicky
>>
>> On 10 August 2012 10:09, Rob Clewley <rob.clewley@gmail.com> wrote:
>> > Hi,
>> >
>> > On Thu, Aug 9, 2012 at 2:15 PM, nicky van foreest <vanforeest@gmail.com>
>> > wrote:
>> >> I am using odeint to integrate the following delay differential
>> >> equation
>> >>
>> >> df/dx = c + f(x) - f(x-1)
>> >>
>> >> somewhat cumbersome. Is it possible in odeint to somehow get
>> >> intermediate values of the function values?
>> >
>> > Nicky, I think your easiest way ahead here is to use a spline to fit
>> > your previous intervals' solution function, building up your solution
>> > using one that meets values and first derivatives at the end points to
>> > retain smoothness as you go. Scipy offers several such spline tools.
>> > Then you can sample that to your heart's content.
>> >
>> > --
>> > Robert Clewley, Ph.D.
>> > Assistant Professor
>> > Neuroscience Institute and
>> > Department of Mathematics and Statistics
>> > Georgia State University
>> > PO Box 5030
>> > Atlanta, GA 30302, USA
>
>
> Depending on the time interval, it might work to treat the equation as a
> Chebyshev series by using its values at the Chebyshev points. Both the
> derivative and the delay are then linear operators that can be represented
> by matrices, see Trefethen's book for the differentiation matrices. The
> boundary conditions might be a bit tricky, but you don't mention how you
> handle the delay there.
>
> Chuck
>
>
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