matlab interp method,matlab函数interp2用法。

interp2

2-D data interpolation (table lookup)

Syntax

ZI = interp2(X,Y,Z,XI,YI)

ZI = interp2(Z,XI,YI)

ZI = interp2(Z,ntimes)

ZI = interp2(X,Y,Z,XI,YI,method)

ZI = interp2(...,method, extrapval)

Description

ZI =

interp2(X,Y,Z,XI,YI) returns matrix ZI containing

elements corresponding to the elements of XI and

YI and determined by interpolation within the

two-dimensional function specified by matrices X,

Y, and Z. X and Y must be

monotonic, and have the same format ("plaid") as if they were

produced by meshgrid. Matrices X and Y

specify the points at which the data Z is given. Out of

range values are returned as NaNs.

XI and YI can be matrices, in which case

interp2 returns the values of Z corresponding to

the points (XI(i,j),YI(i,j)). Alternatively, you can pass

in the row and column vectors xi and yi,

respectively. In this case, interp2 interprets these

vectors as if you issued the command meshgrid(xi,yi).

ZI =

interp2(Z,XI,YI) assumes that X = 1:n and Y =

1:m, where [m,n] = size(Z).

ZI =

interp2(Z,ntimes) expands Z by interleaving

interpolates between every element, working recursively for

ntimes. interp2(Z) is the same as

interp2(Z,1).

ZI =

interp2(X,Y,Z,XI,YI,method) specifies an alternative

interpolation method:

'nearest'

Nearest neighbor interpolation

'linear'

Linear interpolation (default)

'spline'

Cubic spline interpolation

'cubic'

Cubic interpolation, as long as data is uniformly-spaced.

Otherwise, this method is the same as 'spline'.

All interpolation methods require that X and Y

be monotonic, and have the same format ("plaid") as if they were

produced by meshgrid. If you provide two monotonic

vectors, interp2 changes them to a plaid internally.

Variable spacing is handled by mapping the given values in

X, Y, XI, and YI to an equally

spaced domain before interpolating. For faster interpolation when

X and Y are equally spaced and monotonic, use the

methods '*linear', '*cubic', '*spline',

or '*nearest'.

ZI =

interp2(...,method, extrapval) specifies a method and a scalar

value for ZI outside of the domain created by X

and Y. Thus, ZI equals extrapval for any

value of YI or XI that is not spanned by

Y or X respectively. A method must be specified

to use extrapval. The default method is

'linear'.

The interp2 command interpolates between data points.

It finds values of a two-dimensional functionunderlying the data at

intermediate points.

Interpolation is the same operation as table lookup. Described

in table lookup terms, the table is tab = [NaN,Y;X,Z] and interp2 looks up the elements of

XI in X, YI

in Y, and, based upon their

location, returns values ZI

interpolated within the elements of Z.