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Re: Differentiation in IDL [message #50649 is a reply to message #50648]

Mon, 16 October 2006 06:54

Wox
Messages: 184
Registered: August 2006

Senior Member

Specify x?

dx = DERIV(x * !dtor,data)

On Mon, 16 Oct 2006 07:49:21 -0600, David Fanning <news@dfanning.com>
wrote:

> Folks,
>
> OK, I'm missing something crucial here.
>
> Suppose I have a sine function:
>
> x = Findgen(360)
> data = Sin(x * !dtor)
> Plot, data
>
> I know that d/dx(sin(x)) = cos(x). So, I would expect
> a cosine looking curve if I differentiate the data above.
>
> dx = DERIV(data)
> OPlot, dx, Linestyle=2
>
> The differentiated curve is almost a straight line! One
> could argue that it might have the correct cosine *shape*
> (squint your eyes a little bit), but the scale is vastly
> different. How come?
>
> Cheers,
>
> David

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[Message index]

		Re: Differentiation in IDL By: David Fanning on Mon, 16 October 2006 07:31
		Re: Differentiation in IDL By: Allan Whiteford on Mon, 16 October 2006 07:26
		Re: Differentiation in IDL By: Braedley on Mon, 16 October 2006 07:15
		Re: Differentiation in IDL By: David Fanning on Mon, 16 October 2006 06:59
		Re: Differentiation in IDL By: David Fanning on Mon, 16 October 2006 06:56
		Re: Differentiation in IDL By: Wox on Mon, 16 October 2006 06:54

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