SURFACE_FIT Function

Standard Library function that determines the polynomial fit to a surface.

result = SURFACE_FIT(array, degree)

array The two-dimensional array of data to which the surface will be fit. The two dimensions do not have to be the same size. The number of data points must be (degree + 1)².

degree The maximum degree of the fit (in one dimension).

result A two-dimensional array of values as calculated from the least-squares fit of the data.

None.

SURFACE_FIT first determines the coefficients of the polynomials in both directions, using the least-squares method of the POLYWARP function. It then uses these coefficients to calculate the data points of the result array.

OPENR, 1, !Data_dir + 'pikeselev.dat'
data = FLTARR(60, 40)
READF, 1, data

; Read in the data from the pikes elevation file.

CLOSE, 1

; Close the input file.

SURFACE, data

; Show the raw data without fitting.

SURFACE, SURFACE_FIT(data, 1)

; Approximate a linear least-squares fit.

SURFACE, SURFACE_FIT(data, 2)

; Do a second-degree polynomial fit.

SURFACE, SURFACE_FIT(data, 3)

; Do a third-degree polynomial fit.

SURFACE, SURFACE_FIT(data, 4)

; Do a forth-degree polynomial fit.

SURFACE, SURFACE_FIT(data, 5)

; Do a fifth-degree polynomial fit.

POLY_FIT, POLYWARP, SURFACE