# linint2_Wrap

Interpolates from a rectilinear grid to another rectilinear grid using bilinear interpolation, and retains metadata.

## Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl" function linint2_Wrap ( xi : numeric, yi : numeric, fi : numeric, fiCyclicX [1] : logical, xo [*] : numeric, yo [*] : numeric, foOption [1] : integer ) return_val : float or double

## Arguments

*xi*

An array that specifies the X coordinates of the *fi*
array. Most frequently, this is a 1D monotonically increasing array
that may be unequally spaced. In some cases, *xi* can be a
multi-dimensional array (see next paragraph). The rightmost dimension
(call it *nxi*) must have at least two elements, and is the
last (fastest varying) dimension of *fi*.

If *xi* is a multi-dimensional array, then each *nxi*
subsection of *xi* must be monotonically increasing, but may be
unequally spaced. All but its rightmost dimension must be the same
size as all but *fi*'s rightmost two dimensions.

For geo-referenced data, *xi* is generally the longitude array.

*yi*

An array that specifies the Y coordinates of the *fi*
array. Most frequently, this is a 1D monotonically increasing array
that may be unequally spaced. In some cases, *yi* can be a
multi-dimensional array (see next paragraph). The rightmost dimension
(call it *nyi*) must have at least two elements, and is the
second-to-last dimension of *fi*.

If *yi* is a multi-dimensional array, then each *nyi*
subsection of *yi* must be monotonically increasing, but may be
unequally spaced. All but its rightmost dimension must be the same
size as all but *fi*'s rightmost two dimensions.

For geo-referenced data, *yi* is generally the latitude array.

*fi*

An array of two or more dimensions. The two rightmost dimensions must
of size *nyi* x *nxi*, and are the dimensions used in the
interpolation. If missing values are present, the attribute
*fi*@_FillValue must be
set appropriately.

*fiCyclicX*

An option to indicate whether the rightmost dimension of *fi*
is cyclic. This should be set to True only if you have global data,
but your longitude values don't quite wrap all the way around the
globe. For example, if your longitude values go from, say, -179.75 to
179.75, or 0.5 to 359.5, then you would set this to True.

*xo*

A one-dimensional array that specifies the X coordinates of the return array. It must be monotonically increasing, but may be unequally spaced.

For geo-referenced data, *xo* is generally the longitude array.

*yo*

A one-dimensional array that specifies the Y coordinates of the return array. It must be monotonically increasing, but may be unequally spaced.

For geo-referenced data, *yo* is generally the latitude array.

*foOption*

Reserved for future use. Currently not used, but set it to 0.

## Return value

The returned value will have the same dimensions as *fi*,
except for the rightmost two dimensions which will have the same
dimension sizes as the lengths of *yo* and *xo*. The
return type will be double if *fi* is double, and float
otherwise.

## Description

**linint2_Wrap** uses bilinear
interpolation to interpolate from
one rectilinear
grid to another. The input grid may be cyclic in the x
direction. The interpolation is first performed in the x direction,
and then in the y direction.

If missing values are present, then **linint2_Wrap** will perform the bilinear
interpolation at all points possible, but will return missing values
at coordinates which could not be used.

If the output coordinates (*xo*,*yo*) are outside those
of the input coordinates (*xi*,*yi*), then the
*fo* values at those coordinates will be set to missing
(i.e. no extrapolation is performed).

**linint2_Wrap** differs from
**linint2_points_Wrap** in that the
former is designed to interpolate from grid-to-grid, while the latter
is designed to interpolate from a grid to specified locations.

This function is identical to the built-in function
**linint2**, except it retains metadata.

## See Also

**linint2**, **linint2_points_Wrap**,
**linint2_points_Wrap**,
**area_conserve_remap**,
**area_conserve_remap_Wrap**,
**linint1_Wrap**,
**linmsg**,
**area_hi2lores**,
**area_hi2lores_Wrap**

## Examples

**Example 1**

Assume *fi* is dimensioned *niy* x *nix* (30 x
80), and that the rightmost dimension is not to be treated as
cyclic. The returned array will be of size *noy* x
*nox*, where *noy* and *nox* are the sizes of the
one-dimensional arrays *xo* and *yo*:

xi = (30,33,35,39,....., 80) [does not have to be equally spaced] yi = (0,1,2,3,....,28,29) xo = (any coordinates between 30 and 80) [inclusive] yo = (any coordinates between 0 and 29) [inclusive] fo =linint2_Wrap(xi,yi,fi, False, xo,yo, 0)

**Example 2**

Assume *fi* is a 4D array dimensioned *ntim* x
*nlvl* x *nlat* x *mlon* (*ntim*=50,
*nlvl*=30, *nlat*=64, *mlon*=128), and that the
rightmost dimension is to be treated as cyclic (the user should not
add a cyclic point for the rightmost dimension).

All times and levels will be interpolated and returned in a new array
*fo* dimensioned *ntim* x *nlvl* x *73* x
*144*:

lon = (0., 2.8125, .... , 357,0125) lat = (-87.8638, ... ,87.8638) LON = (0., 2.5, ... , 357.5) ; length 144 LAT = (-90.,87.5,...90.) ; length 73 fo =linint2_Wrap(lon,lat,fi, True, LON,LAT, 0)