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Re: An approximation of the cumulative integral of Y [message #67308 is a reply to message #67304]

Sat, 11 July 2009 10:07

Vince Hradil
Messages: 574
Registered: December 1999

Senior Member

On Jul 11, 11:43 am, Vince Hradil <vincehra...@gmail.com> wrote:
> On Jul 11, 12:39 am, Vijay Shah <vijayps...@gmail.com> wrote:
>
>> Hi,
>> Is there any subroutine in IDL that allows to computes an
>> approximation of the cumulative integral of Y via the trapezoidal
>> method (with unit spacing)?
>
>> Regards,
>> Vijay
>
> INT_TABULATED() works nicely (not really what you want, but better?)
>
> It would be easy enough to write using SHIFT(). Something like
>
> y2 = (y+shift(y,1))/2
> x2 = (x+shift(x,1))/2
> integral = total(x2*y2); or total(x2*y2,/cumulative)
>
> You have to figure out how to deal with the "ends" from the shift...

Let's see, I think that should be:
x2 = x-shift(x,1)
or use delta x if it doesn't change

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[Message index]

		Re: An approximation of the cumulative integral of Y By: Vijay Shah on Mon, 13 July 2009 22:23
		Re: An approximation of the cumulative integral of Y By: Jeremy Bailin on Sun, 12 July 2009 13:00
		Re: An approximation of the cumulative integral of Y By: Chris[6] on Sun, 12 July 2009 12:40
		Re: An approximation of the cumulative integral of Y By: Vijay Shah on Sun, 12 July 2009 08:58
		Re: An approximation of the cumulative integral of Y By: Vince Hradil on Sat, 11 July 2009 10:07
		Re: An approximation of the cumulative integral of Y By: Vince Hradil on Sat, 11 July 2009 09:43

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