[SciPy-User] cumtrapz

Nils Wagner nwagner@iam.uni-stuttgart...
Thu Nov 4 08:29:21 CDT 2010


On Thu, 4 Nov 2010 08:20:27 -0500
  Ryan May <rmay31@gmail.com> wrote:
> On Thu, Nov 4, 2010 at 3:42 AM, Nils Wagner
> <nwagner@iam.uni-stuttgart.de> wrote:
>> Hi all,
>>
>> cumtrapz can be used to compute the antiderivative.
>>
>> x = linspace(0,2*pi,200)
>> y = 2*cos(2*x)
>> Y = cumtrapz(y,x)
>>
>>
>>
>> len(y) = 200
>> len(Y) = 199
>>
>> The length of the arrays y and Y differ by one. For what
>> reason ?
> 
> Because when integrating using the trapezoid rule, you 
>are forming N-1
> trapezoids from N datapoints.
> 
> Ryan
> 
> -- 
> Ryan May
> Graduate Research Assistant
> School of Meteorology
> University of Oklahoma
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Hi Ryan,

is there an integration rule in scipy that preserves the 
length of the input array ?

I would to integrate an acceleration signal twice to 
obtain the displacement.

v = \int a dt = \int dv
u = \int v dt  = \int du

Nils


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