CLsqFit:GetCoef

The GetCoef method returns the value of a fit coefficient.

Syntax

nValue = CLsqFit:GetCoef( nIndex )

nValue = CLsqFit:GetCoef( nIndex, nChan )

nV1, nV2, nV3, nV4 = CLsqFit:GetCoef( nIndex )

where

nIndex is a number between 1 and GetNumCoefs().

nValue is the returned value of the coefficient.

nChan is an optional argument that specifies the channel for multi-channel (RGB) data.

nV1, nV2, nV3, and nV4 are values returned for multi-channel data when no channel is specified.

This function returns the coefficient at the specified index. If multi-channel data has been enabled, then values are returned for all channels unless you specifically specify a channel. The errors of the coefficients can be obtained using GetCoefErr and the covariance between coefficients can be obtained using GetCovar.

If using the built-in n-dimensional polynomial basis function with n > 1, then the index of the coefficient must be determined by calculating it from the polynomial dimensions or by using GetPolyCoefIndex.

Example

The following script retrieves the constant valued coefficient at index 1,1 after doing a 2x2 polynomial fit. The n-dimensional polynomial is selected by default and no other basis function is specified using SetBasisFunc. As with all sample scripts, this script is very wordy for for purposes of clarity and the statements near the end could be more tightly coded.

L = CLsqFit:new()	-- create a CLsqFit object
L:SetNumCoefs( {2.2} )	-- set 2x2 coefficients to fit a warped plane
L:AddPt( {3, 5}, 5.15 )	-- add a point with x = 3, y = 5, z = 5.15
	-- add more points
L:Fit()	-- Fit the polynomial
i = 1 j = 1	-- select coefficient at 1, 1
n = L:GetPolyCoefIndex( i, j )	-- fetch the index of the coefficient at i, j
v = L:GetCoef( n )
Printf( "Coef[%d][%d]= %lg\n", i, j, v )	-- list the coefficient value