[SciPy-Dev] griddata equivalent of matlab "V4" option

[Alexandre Gramfort]

hi,

scipy does not seem to implement the griddata V4 option from matlab.

The original reference is :

David T. Sandwell, Biharmonic spline interpolation of GEOS-3 and
SEASAT altimeter data, Geophysical Research Letters, 2, 139-142, 1987.

is there a reason for it?

should I look for it somewhere else?

thanks
Alex

[Pauli Virtanen]

Post by Alexandre Gramfort
scipy does not seem to implement the griddata V4 option from matlab.
David T. Sandwell, Biharmonic spline interpolation of GEOS-3 and
SEASAT altimeter data, Geophysical Research Letters, 2, 139-142, 1987.
is there a reason for it?

Is there a good reason to implement it?

[Alexandre Gramfort]

Post by Pauli Virtanen
Is there a good reason to implement it?

I need to produce images like:

Loading Image...

the black dots are the sensors where measurements are done.

the interpolation needs to extrapolate a tiny bit to fill the circle
although the sensors are a little inside. The options of griddata
don't do the job. cubic cannot extrapolate and nearest is not nice.

Alex

[Davide Lasagna]

Do you by chance happen to know the value on the circle? Because you could
add some artificial points and use whatever SciPy provides.

Davide

Post by Alexandre Gramfort

Post by Pauli Virtanen
Is there a good reason to implement it?

http://fieldtrip.fcdonders.nl/_media/tutorial/plotting/figure4.png?cache=&w=568&h=496
the black dots are the sensors where measurements are done.
the interpolation needs to extrapolate a tiny bit to fill the circle
although the sensors are a little inside. The options of griddata
don't do the job. cubic cannot extrapolate and nearest is not nice.
Alex
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[Alexandre Gramfort]

Post by Davide Lasagna
Do you by chance happen to know the value on the circle? Because you could
add some artificial points and use whatever SciPy provides.

no I don't. In the mean time we reimplemented this algorithm.

let me know if it shall be pushed to scipy.

Alex

[Nathaniel Smith]

On Sat, Jul 5, 2014 at 8:12 PM, Alexandre Gramfort

Post by Alexandre Gramfort

Post by Davide Lasagna
Do you by chance happen to know the value on the circle? Because you could
add some artificial points and use whatever SciPy provides.

no I don't. In the mean time we reimplemented this algorithm.
let me know if it shall be pushed to scipy.

I'm not a scipy dev, but I am interested in the functionality, so if
your code is a good way to provide it then I'd vote for submitting a
PR to scipy :-)

[Denis A. Engemann]

Cool, I'll a open a PR tomorrow if no one is objected.

Post by Nathaniel Smith
On Sat, Jul 5, 2014 at 8:12 PM, Alexandre Gramfort

Post by Alexandre Gramfort

Post by Davide Lasagna
Do you by chance happen to know the value on the circle? Because you could
add some artificial points and use whatever SciPy provides.

no I don't. In the mean time we reimplemented this algorithm.
let me know if it shall be pushed to scipy.

I'm not a scipy dev, but I am interested in the functionality, so if
your code is a good way to provide it then I'd vote for submitting a
PR to scipy :-)
--
Nathaniel J. Smith
Postdoctoral researcher - Informatics - University of Edinburgh
http://vorpus.org
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[Alex Liberzon]

I believe the Radial Basis Function can do the work:

http://wiki.scipy.org/Cookbook/RadialBasisFunctions

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1. Re: griddata equivalent of matlab "V4" option (Pauli Virtanen)
2. Re: griddata equivalent of matlab "V4" option (Alexandre Gramfort)
3. Re: griddata equivalent of matlab "V4" option (Davide Lasagna)
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Message: 1
Date: Fri, 04 Jul 2014 21:59:50 +0300
Subject: Re: [SciPy-Dev] griddata equivalent of matlab "V4" option
Content-Type: text/plain; charset=ISO-8859-1

Post by Alexandre Gramfort
scipy does not seem to implement the griddata V4 option from matlab.
David T. Sandwell, Biharmonic spline interpolation of GEOS-3 and
SEASAT altimeter data, Geophysical Research Letters, 2, 139-142, 1987.
is there a reason for it?

Is there a good reason to implement it?
--
Pauli Virtanen
------------------------------
Message: 2
Date: Fri, 4 Jul 2014 21:38:22 +0200
Subject: Re: [SciPy-Dev] griddata equivalent of matlab "V4" option
<
Content-Type: text/plain; charset=UTF-8

Post by Alexandre Gramfort
Is there a good reason to implement it?

http://fieldtrip.fcdonders.nl/_media/tutorial/plotting/figure4.png?cache=&w=568&h=496
the black dots are the sensors where measurements are done.
the interpolation needs to extrapolate a tiny bit to fill the circle
although the sensors are a little inside. The options of griddata
don't do the job. cubic cannot extrapolate and nearest is not nice.
Alex
------------------------------
Message: 3
Date: Sat, 5 Jul 2014 11:36:24 +0100
Subject: Re: [SciPy-Dev] griddata equivalent of matlab "V4" option
<CAOF5zP5qcu=o05=
Content-Type: text/plain; charset="utf-8"
Do you by chance happen to know the value on the circle? Because you could
add some artificial points and use whatever SciPy provides.
Davide

Post by Alexandre Gramfort

Post by Pauli Virtanen
Is there a good reason to implement it?

http://fieldtrip.fcdonders.nl/_media/tutorial/plotting/figure4.png?cache=&w=568&h=496

Post by Alexandre Gramfort
the black dots are the sensors where measurements are done.
the interpolation needs to extrapolate a tiny bit to fill the circle
although the sensors are a little inside. The options of griddata
don't do the job. cubic cannot extrapolate and nearest is not nice.
Alex
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http://mail.scipy.org/mailman/listinfo/scipy-dev

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