BivariateInterpolation {fUtilities}R Documentation

Bivariate Interpolation

Description

A collection and description of functions which allow to interpolate and smooth bivariate irregular data sets including linear interpolation, Akima spline interpolation, and kriging.

Gridded Interpolation Functions:

linearInterp performs linear spline interpolation,
akimaInterp performs Akima spline interpolation,
krigeInterp performs krige interpolation.

Pointwise Interpolation Functions:

linearInterpp performs linear spline interpolation,
akimaInterpp performs Akima spline interpolation

Usage

 
linearInterp(x, y = NULL, z = NULL, gridPoints = 21,
    xo = seq(min(x), max(x), length = gridPoints),
    yo = seq(min(y), max(y), length = gridPoints))
linearInterpp(x, y = NULL, z = NULL, xo, yo)
     
akimaInterp(x, y = NULL, z = NULL, gridPoints = 21,
    xo = seq(min(x), max(x), length = gridPoints),
    yo = seq(min(y), max(y), length = gridPoints), extrap = FALSE)
akimaInterpp(x, y = NULL, z = NULL, xo, yo, extrap = FALSE)

krigeInterp(x, y = NULL, z = NULL, gridPoints = 21,
    xo = seq(min(x), max(x), length = gridPoints),
    yo = seq(min(y), max(y), length = gridPoints), 
    extrap = FALSE, polDegree = 6)

Arguments

x, y, z [griddata] -
x and y are two numeric vectors of grid pounts and z is a numeric matrix or any other rectangular object which can be transformed by the function as.matrix into a matrix object.
[akimaInterp][krigeInterp] -
either three numeric vectors of equal length or if y and z are NULL, a list with entries x, y, z, or named data frame with x in the first, y in the second, and z in the third column.
[persp][contour] -
x is an pbject of class gridData.
gridPoints an integer value specifying the number of grid points in x and y direction.
xo, yo [*Interp] -
two numeric vectors of data points spanning the grid.
[*Interpp] -
two numeric vectors of data points building pairs for pointwise interpolation.
extrap a logical, if TRUE then the data points are extrapolated.
polDegree [krige] -
the polynomial krige degree, an integer ranging between 1 and 6.

Value

linearInterp -
akimaInterp -
krigeInterp -
A list with at least three entries, x, y and z. Note, that the returned values, can be directly used by the persp.gridData() and contour.gridData 3D plotting methods.
linearInterpp -
akimaInterpp -
A data.frame with columns "x", "y", and "z".

Note

The function krigeInterp requires loading of the R package spatial.

IMPORTANT: The contributed package akima is not in the dependence list of the DESCRIPTION file due to license conditions. The Rmetrics user has to load this package from the CRAN server on his own responsibility, please check the license conditions.

Author(s)

Diethelm Wuertz for the Rmetrics R-port,
H. Akima for the Fortran Code of the Akima spline interpolation routine.

Examples

 
## Not run: 
## akimaInterp -
   # Akima Interpolation:    
   set.seed(1953)
   x = runif(999) - 0.5
   y = runif(999) - 0.5
   z = cos(2*pi*(x^2+y^2))
   ans = akimaInterp(x, y, z, extrap = FALSE)
   persp(ans)
   contour(ans)
   
## krigeInterp -
   # Kriging:    
   ans = krigeInterp(x, y, z, extrap = FALSE)
   persp(ans)
   contour(ans)
## End(Not run)

[Package fUtilities version 260.72 Index]