polyfit Documentation

polyfit - Find coefficients of polynomial fit at each pixel
This program creates an output cube of polynomial coefficients for
the "best fit" for a polynomial relating the dn value to the "x"
values at each band.  The "x" values are given in the XFILE and
define the distance along the x-axis for each band.  An example of
possible "x" values could be the wave-length of each band.
Polynomial coefficients are found at every line and sample position of
the input cube.  The equation to be fit is:

  y=c(1) + c(2)*x + c(3)*x**2 + c(4)*x**3 . . .+ c(10)*x**9

Where y is the predicted dn (brightness value) for a given "x".

The output cube is 32 bit and has DEG+5 bands.  The first band contains
c(1), the second band contains c(2), etc thru DEG+1 bands.
DEG+2 contains the minimum value at each pixel.
DEG+3 contains the maximum value at each pixel.
DEG+4 contains the average fit error at each pixel.
DEG+5 contains the standard deviation of the fit error at each pixel.

Programmer: Kay Edwards  U.S.G.S. Flagstaff

Input cube file name
(default extension is .cub)

NONE

Output cube file name
(default extension is .cub)

NONE

X-axis file
(no default extension)

NONE

Degree of polynomial fit
(1-9)

3

Min/Max core data range

1,250

ADDITIONAL NOTES:

Parm	Description
FROM	Input cube file name. If the file extension is omitted, then ".cub" will be assumed.
TO	Output cube file name. If the file extension is omitted, then ".cub" will be assumed.
XFILE	Ascii file containing X-axis values for polynomial fit. The file must contain one x value per line and there must be the same number of x values as bands in the cube.
DEG	A least-squares fit to a polynomial will be made on the dn values of all bands at each line and sample position ignoring any special pixel values. See the main program description for more detail.
CRANGE	The minimum and maximum valid values of the core data. Any data that falls outside this range will not be used in the polynomial fit.