MATLAB Function Reference |

Data gridding and hypersurface fitting (dimension >= 2)

**Syntax**

yi = griddatan(X,y,xi) yi = griddatan(

`x,y,z,v,xi,yi,zi`

,method)`yi = griddatan(x,y,z,v,xi,yi,zi,method,options)`

**Description**

```
yi = griddatan(X, y, xi)
```

fits a hyper-surface of the form to the data in the (usually) nonuniformly-spaced vectors (`X`

, `y`

). `griddatan`

interpolates this hyper-surface at the points specified by `xi`

to produce `yi`

. `xi`

can be nonuniform.

`X`

is of dimension `m`

-by-`n`

, representing `m`

points in n-dimensional space. `y`

is of dimension `m`

-by-`1`

, representing `m`

values of the hyper-surface (`X`

). `xi`

is a vector of size `p`

-by-`n`

, representing `p`

points in the n-dimensional space whose surface value is to be fitted. `yi`

is a vector of length `p`

approximating the values (`xi`

). The hypersurface always goes through the data points (`X`

,`y`

). `xi`

is usually a uniform grid (as produced by `meshgrid`

).

`yi = griddatan(`

defines the type of surface fit to the data, where `x,y,z,v,xi,yi,zi`

,method)
`'method'`

is one of:

`'linear'` |
Tessellation-based linear interpolation (default) |

`'nearest'` |
Nearest neighbor interpolation |

All the methods are based on a Delaunay tessellation of the data.

If `method`

is `[]`

, the default `'linear'`

method is used.

`yi = griddatan(x,y,z,v,xi,yi,zi,method,options)`

specifies a cell array of strings `options`

to be used in Qhull via `delaunayn`

.

If `options`

is `[]`

, the default options are used. If `options`

is `{''}`

, no options are used, not even the default.

**Algorithm**

The `griddatan`

methods are based on a Delaunay triangulation of the data that uses Qhull [2]. For information about Qhull, see http://www.qhull.org/. For copyright information, see http://www.qhull.org/COPYING.txt.

**See Also**

`delaunayn`

, `griddata`

, `griddata3`

, `meshgrid`

**Reference**

[1] Barber, C. B., D.P. Dobkin, and H.T. Huhdanpaa, "The Quickhull Algorithm for
Convex Hulls," *ACM Transactions on Mathematical Software*, Vol. 22, No. 4,
Dec. 1996, p. 469-483. Available in HTML format at
http://www.acm.org/pubs/citations/journals/toms/1996-22-4/p469-barber.

[2] National Science and Technology Research Center for Computation and Visualization of Geometric Structures (The Geometry Center), University of Minnesota. 1993.

griddata3 | gsvd |

© 1994-2005 The MathWorks, Inc.