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Re: how can one use mathematica get the approximate derivative of {x,y} data points?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124241] Re: how can one use mathematica get the approximate derivative of {x,y} data points?
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Sat, 14 Jan 2012 17:07:59 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <jercda$19h$1@smc.vnet.net>

"Michael B. Heaney" wrote:

> Hi,
>
> I have a set of {x,y} data points:
>
>  {{0.03512, -0.5}, {0.0351181, -0.499}, ... {-0.113972, 0.699}, {-0.115072,
> 0.7}}
>
> These data points look like a function y=f(x) when plotted on the x-y axes.
> However, I do not know what the function f(x) is. But I need to get the
> approximate derivative df/dx, as another set of data points. How can one
> use Mathematica to do this?
>
> Thanks,
>
> Michael
>
> --

You can try Interpolation.

fun[x_]:=x^2Cos[x]

These will give approximate data for this function:

data=Table[{x,fun[x]+RandomReal[{0,0.25}]},{x,0,1,0.5}]

iF=Interpolation[data]

Derivative:

iF'[3]

Plot[{iF[x],iF'[x]},{x,0,5}]


-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de



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