do you really require equally spaced grids?

[floswald]

hello,

i've just read through the GSL 2.1 manual: https://www.gnu.org/software/gsl/manual/html_node/2D-Introduction-to-Interpolation.html#g_t2D-Introduction-to-Interpolation

where it says that one needs two equally spaced grids x and y to use the functions for 2D interpolation. Is that true? thanks.

[tbeu]

Not to my knowledge. What is needed is a regular grid.

[floswald]

And by regular grid you mean that there are n points for x, m points for y,
and nm points for z =f(x,y)?

On Monday, 18 January 2016, tbeu notifications@github.com wrote:

Not to my knowledge. What is needed is a regular grid.

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[tbeu]

exactly

[floswald]

ok that's somewhat reassuring - at least that's how it should work in both
of our minds. I'd like to know for sure though from @diazona ? the GSL doc
is very confusing there.

On 18 January 2016 at 21:05, tbeu notifications@github.com wrote:

exactly

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[diazona]

Indeed, the grid does not need to be equally spaced, it only needs to be rectangular. (@tbeu is right; he's worked with this code base at least as much as I have so he knows it very well.) There is actually one test which uses this feature.

@floswald I'd suggest sending a message to the GSL mailing list about this. Or if you don't want to, I can do it.

[floswald]

ok good stuff. yeah if you don't mind sending that email - i'm not
subscribed.

cheers

On 19 January 2016 at 10:42, David Zaslavsky notifications@github.com
wrote:

Indeed, the grid does not need to be equally spaced, it only needs to be
rectangular. (@tbeu https://github.com/tbeu is right; he's worked with
this code base at least as much as I have so he knows it very well.) There
is actually one test
https://github.com/diazona/interp2d/blob/master/test.c#L277 which uses
this feature.

@floswald https://github.com/floswald I'd suggest sending a message to
the GSL mailing list about this. Or if you don't want to, I can do it.

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#8 (comment).

[diazona]

OK, email sent. I'll continue to follow up on this, but seeing as how this is an issue with GSL, not with interp2d, I'll close it here.