Bivariate Interpolation for Data on a Rectangular grid
The description in the Fortran code says:
This subroutine performs interpolation of a bivariate function, z(x,y), on a rectangular grid in the x-y plane. It is based on the revised Akima method.
In this subroutine, the interpolating function is a piecewise function composed of a set of bicubic (bivariate third-degree) polynomials, each applicable to a rectangle of the input grid in the x-y plane. Each polynomial is determined locally.
This subroutine has the accuracy of a bicubic polynomial, i.e., it interpolates accurately when all data points lie on a surface of a bicubic polynomial.
The grid lines can be unevenly spaced.
bicubic(x, y, z, x0, y0)
x |
a vector containing the |
y |
a vector containing the |
z |
a matrix containing the |
x0 |
vector of |
y0 |
vector of |
This functiuon is a R interface to Akima's Rectangular-Grid-Data Fitting algorithm (TOMS 760). The algorithm has the accuracy of a bicubic (bivariate third-degree) polynomial.
This function produces a list of interpolated points:
x |
vector of |
y |
vector of |
z |
vector of interpolated data |
If you need an output grid, see bicubic.grid.
Use interp for the general case of irregular gridded data!
Akima, H. (1996) Rectangular-Grid-Data Surface Fitting that Has the Accuracy of a Bicubic Polynomial, J. ACM 22(3), 357-361
data(akima760)
# interpolate at the diagonal of the grid [0,8]x[0,10]
akima.bic <- bicubic(akima760$x,akima760$y,akima760$z,
seq(0,8,length=50), seq(0,10,length=50))
plot(sqrt(akima.bic$x^2+akima.bic$y^2), akima.bic$z, type="l")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.