comp.lang.idl-pvwave archive: archive

Home » Public Forums » archive » Derivatives

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Derivatives [message #86555 is a reply to message #86553]

Tue, 19 November 2013 02:49

Mats Löfdahl
Messages: 263
Registered: January 2012

Senior Member

Den tisdagen den 19:e november 2013 kl. 11:20:40 UTC+1 skrev fd_...@mail.com:
> Hi
>
> I want to use the simple differentiation formula instead of DERIV function( 3-point, Lagrangian interpolation):
>
> Derivative=change in y/change in x
>
> I wrote my code like this but my results are absolutely wrong and I don't see where my mistake is.
>
> derivative= (A[1:*]-A)/ (t[1:*]-t)
> derivative=[0,derivative]

Looks OK to me. In what way is the result "absolutely wrong"?

> I did the last step i.e. derivative=[0,derivative] because I need an array[2001,1] instead of array[2000,1].

I'm not sure why you expect a two-dimensional array but adding an element seems appropriate, since you removed one by doing selecting 1:*. I don't know how much sense it makes to add a zero (derivative =[derivative[0],derivative] might be more useful) but you are the only who knows your data.

Report message to a moderator

[Message index]

		Derivatives By: fd_luni on Tue, 19 November 2013 02:20
		Re: Derivatives By: Mats Löfdahl on Tue, 19 November 2013 02:49
		Re: Derivatives By: fd_luni on Tue, 19 November 2013 07:23
		Re: Derivatives By: Craig Markwardt on Tue, 19 November 2013 18:45

Previous Topic:	Time conversion for .nc file
Next Topic:	_EXTRA KEYWORD

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 19:29:46 PDT 2025

Total time taken to generate the page: 0.00397 seconds