| Re: spatial interpolation [message #36522] |
Fri, 03 October 2003 04:07  |
Richard French
Messages: 173
Registered: December 2000
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Senior Member |
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On 10/3/03 6:32 AM, in article
e1330fff.0310030232.52e4cea4@posting.google.com, "Hjalti Sig"
<hjalti@vatnaskil.is> wrote:
> Thank you so much. The description for this function in the reference
> guide does not mention this - only regular grids. And the only
> possible return value mentioned is a two dimensional array. This is
> somewhat misleading.
> Regards, Hjalti
>
I've just looked this up in the IDL6.0 manual and the KEYWORDS XOUT and YOUT
(NOT the same as a returned value of a function) are definitely described,
albeit in the midst of about another 20 definitions for other keywords. So,
I don't find it misleading, but it does show that you need to read through
the documentation with great care to see the capabilities of some of the
more complex IDL procedures/functions such as AXIS.
I hope GRIDDATA does what you need.
Dick French
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| Re: spatial interpolation [message #36613 is a reply to message #36522] |
Sun, 05 October 2003 14:18  |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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Richard G. French wrote:
> On 10/3/03 6:32 AM, in article
> e1330fff.0310030232.52e4cea4@posting.google.com, "Hjalti Sig"
> <hjalti@vatnaskil.is> wrote:
>
>> Thank you so much. The description for this function in the reference
>> guide does not mention this - only regular grids. And the only
>> possible return value mentioned is a two dimensional array. This is
>> somewhat misleading.
>
> I've just looked this up in the IDL6.0 manual and the KEYWORDS XOUT and YOUT
> (NOT the same as a returned value of a function) are definitely described,
> albeit in the midst of about another 20 definitions for other keywords. So,
> I don't find it misleading, but it does show that you need to read through
> the documentation with great care to see the capabilities of some of the
> more complex IDL procedures/functions such as AXIS.
Great care and a grain or two of salt.
The opening sentence of the GRIDDATA documentation says:
The GRIDDATA function interpolates scattered data values and
locations sampled on a plane or a sphere to a regular grid.
This is true, but incomplete. As noted, GRIDDATA also does interpolation
onto irregular grids and scattered data points.
And the "return value" section says
The function result is a two-dimensional floating point array.
This is just plain wrong. It can also return 1-D output data.
A documentation bug report to RSI is warranted. Any volunteers? (They're
tired of hearing from me.)
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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