Interpolation/
fromreg.pro
interpolate data from a "regular/rectangular grid" to any grid.
2 methods available: bilinear and imoms3
A "regular/rectangular grid" is defined as a grid for which
each longitude lines have the same latitude and each latitude columns
have the same longitude.
fromreg
Interpolation
result = fromreg(method, datain, lonin, latin, lonout, latout, WEIG=2d array or variable name, ADDR=2d array or variable name, NONORTHERNLINE=NONORTHERNLINE, NOSOUTHERNLINE=NOSOUTHERNLINE, _EXTRA=_EXTRA)
Return value
2D array the interpolated data
Parameters
method
in
required
type: string
the interpolation method.
must be 'bilinear' or 'imoms3'
datain
in
required
type: 2d array
the input data to interpolate
lonin
in
required
type: 1d or 2d array
the longitude of the input data
latin
in
required
type: 1d or 2d array
the latitude of the input data
lonout
in
required
type: 1d or 2d array
the longitude of the output data
latout
in
required
type: 1d or 2d array
the latitude of the output data
Keywords
WEIG
type: 2d array or variable name
(see ADDR)
ADDR
type: 2d array or variable name
1) at the first call of fromreg:
This keyword can be set to a named variable (undefined or equal to 0) into which the
addresses used to perform the interpolation will be copied when the current routine exits.
2) Next, once this keyword is set to a defined 2d array, it is used to bypass the computation
of the weights and addresses used to perform the interpolation. In this case, fromreg simply
compute the interpolated field as:
dataout = total(weig*datain[addr], 1)
dataout = reform(dataout, jpio, jpjo, /over)
In that case, method, lonin, latin, are not used (but are necessary).
lonout, latout are used only to know the output domain size
NONORTHERNLINE
activate if you don't want to take into account the northern line
of the input data when performing the interpolation.
NOSOUTHERNLINE
activate if you don't want to take into account the southern line
of the input data when performing the interpolation.
_EXTRA
to be able to call fromreg with _extra keyword
Examples
To interpolate 1 field:
IDL> topa = fromreg('bilinear', tncep, xncep, yncep, glamt, gphit)
or if you have several fields to interpolate from the same source and target grids
1) get back the weights and addresses in variables a and b
(that must be undefined or equal to 0 before calling fromreg
IDL> t1opa = fromreg('bilinear', t1ncep, xncep, yncep, glamt, gphit, WEIG = a, ADDR = b)
IDL> help, a, b
2) use a and b that are now defined to bypass the computation of the weights and addresses
and speed-up the computation!
IDL> t2opa = fromreg('bilinear', t2ncep, xncep, yncep, glamt, gphit, WEIG = a, ADDR = b)
Version history
Version
$Id: fromreg.pro 327 2007-12-13 16:22:35Z pinsard $
History
November 2005: Sebastien Masson (smasson@lodyc.jussieu.fr)
Known issues
Restrictions
We supposed the data are located on a sphere, with a periodicity along the
longitude.
Produced by IDLdoc 2.0.
