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MathGroup Archive 2007

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Re: How to calculate gradient and laplace of a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72880] Re: How to calculate gradient and laplace of a list
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 24 Jan 2007 05:18:02 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <ep4kd5$rat$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

you can only compute the derivative (or the second derivative, or the 
gradient) of a smooth function and not from discrete data.

If you have a equdistant grid, you may use a discrete approximation
of a derivative -- a finte difference expression, or you may construct
an interpolation function ancd compute the derivative of the 
interpolated function.

And vector field can be drawn with PlotField[]

Regards
    Jens

leoshen wrote:
> Hi, guys
> I have a matrix of n*m read from a file. mathematica has built in function 
> to do discrete fourier transform of the list.
> Can I calculate the gradient and the laplace of the matrix?
> I can use the listcontourplot to plot the matrix, Is there any way to plot 
> the gradient plot of it?
> 
> 
> 
> 


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