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Check numerical derivatives [message #94527]

Tue, 27 June 2017 03:30

geo85c
Messages: 4
Registered: June 2017

Junior Member

Hi there,

I wanted to calculate numerical derivatives of a function. I would like to check if the following are correct.

Consider the function F in R^2.
F is a 2D image.
I did the following:
dims = size(F, /dimensions)
nx = dims[0]
ny = dims[1]
xc = findgen(nx)
yc = findgen(ny)

Derivative with respect to x:
F_x = F[xc[1:nx-1],*]-F[xc[0:nx-2],*] ;first order deriv
F_xx = F_x[xc[1:nx-1],*]-F[xc[0:nx-2],*] ;second order deriv
F_y = F[*,yc[1:ny-1]] - F[*,yc[0:ny-2]]
F_xy = F_x[*,yc[1:ny-1]] - F_x[*,yc[0:ny-2]]

Then I wanted to differentiate F_xy with respect to x. I did the following:
F_xxy = F_xy[xind[1:nx-1],*] - F_xy[xind[0:nx-2],*]

Are the above correct?

Thanks.

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[Message index]

		Check numerical derivatives By: geo85c on Tue, 27 June 2017 03:30
		Re: Check numerical derivatives By: wlandsman on Tue, 27 June 2017 07:52
		Re: Check numerical derivatives By: geo85c on Wed, 28 June 2017 01:23
		Re: Check numerical derivatives By: wlandsman on Wed, 28 June 2017 07:46

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