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Re: derivative function in IDL similar as DIFF in matlab [message #86466 is a reply to message #86464]

Tue, 12 November 2013 04:08

Matthew Argall
Messages: 286
Registered: October 2011

Senior Member

On Tuesday, November 12, 2013 7:01:15 AM UTC-5, Matthew Argall wrote:
> On Tuesday, November 12, 2013 5:08:11 AM UTC-5, Jie Zhou wrote:
>
>> Is there a derivative function in IDL similar as DIFF in matlab? I think the DERIV is different from DIFF.
>
>
>
> TS_DIFF(data, 1) would be equivalent.

Actually, maybe not. TS_DIFF calculates the forward difference. I think you are looking for the backward difference.

In that case, I tend to use

result = data[1:*] - data[0:n_elements(data)-1]

or

result = shift(data, 1) - data
result = result[0:n_elements(result)-1]

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[Message index]

		derivative function in IDL similar as DIFF in matlab By: Jie Zhou on Tue, 12 November 2013 02:08
		Re: derivative function in IDL similar as DIFF in matlab By: lecacheux.alain on Tue, 12 November 2013 02:27
		Re: derivative function in IDL similar as DIFF in matlab By: Matthew Argall on Tue, 12 November 2013 04:01
		Re: derivative function in IDL similar as DIFF in matlab By: lecacheux.alain on Tue, 12 November 2013 04:07
		Re: derivative function in IDL similar as DIFF in matlab By: Matthew Argall on Tue, 12 November 2013 04:08
		Re: derivative function in IDL similar as DIFF in matlab By: Jie Zhou on Tue, 12 November 2013 04:18
		Re: derivative function in IDL similar as DIFF in matlab By: Matthew Argall on Tue, 12 November 2013 06:07

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