2.1.11.2 Fitpoly

1 Description
2 Syntax
3 Parameters
4 Return
5 Examples
6 Remark
7 See Also
8 Header to Include
9 Reference

Description

Fit a polynomial equation to XY vectors and return the coefficients and statistical results.

Fit a polynomial equation to a curve and return the coefficients and statistical results.

Fit a polynomial equation to a curve or curve segment.

Fit a polynomial equation to a curve or curve segment and return the parameter coefficients.

Syntax

bool fitpoly( vector & vX, vector & vY, int nOrder, vector & pCoeff = NULL, vector & pError = NULL, RegStats * psRegStats = NULL )

bool fitpoly( Curve & cv, int nOrder, vector & pCoeff = NULL, vector & pError = NULL, RegStats * psRegStats = NULL, int iBeg = 0, int iEnd = -1, double * pxmin = NULL, double * pxmax = NULL )

BOOL fitpoly( Curve & crv, int ipolyorder, double * coeff, int inumer = 0, int idenom = 0 )

int fitpoly( int nOrder, double * pX, double * pY, int nSize, vector & vCoeff, vector & vError = NULL, RegStats * psRegStats = NULL, bool * pbXNorm = NULL, LROptions* pstLROptions = NULL )

Parameters

vX: [input] vector containing data points of the independent variables
vY: [input] vector containing data points of the dependent variables
nOrder: [input] degree of polynomial equation
pCoeff: [output] vector containing parameter coefficients
pError: [output] vector containing parameter errors
psRegStats: [output] struct containing statistical results, such as Chi^2 etc.

cv: [input] curve to fit
nOrder: [input] degree of polynomial equation
pCoeff: [output] vector containing parameter coefficients
pError: [output] vector containing parameter errors
psRegStats: [output] struct containing statistical results, such as Chi^2 etc.
iBeg: [input] beginning index of data points to fit. Index values are 0 based. The default value 0 refers to the lower bound.
iEnd: [input] ending index of data points to fit. Index values are 0 based. The default value -1 refers to the upper bound.
pxmin: [output] pointer to min x in range
pxmax: [output] pointer to max x in range

crv: [input] curve to fit
ipolyorder: [input] degree of polynomial equation
coeff: [output] array containing parameter coefficients
inumer: [input] Nth segment of M equal curve segments (default 0 fits entire range as one segment)
idenom: [input] number M of equal curve segments (default 0 fits entire range as one segment)

nOrder: [input] Degree of polynomial equation, nOrder >= 1
pX: [input] Vector containing data points of the independent variables, size of pX = nSize
pY: [input] Vector containing data points of dependent variable, size of pY = nSize
nSize: [input] The number of observations, n. n>=2
vCoeff: [output] Vector containing parameter coefficients
vError: [output] Vector containing parameter errors
psRegStats: [output] Struct containing statistical results, such as Chi^2 etc
pbXNorm: [output] true for performing normalization on the source data in the case of source data have large absolute value but relative small range. false for other case.
pstLROptions: [input] Input pointer to struct for linear regression options.

Return

Returns TRUE on success and FALSE on failure.

Returns STATS_NO_ERROR or positive on successful exit and a negative STATS error code on failure.

LARGE_X_NORMALIZED(1): the independent data have large value and small range, so are normalized first.

Error Codes:

STATS_INPUT_NULL_POINTER(-156): pX and pY must not be empty.

STATS_ERROR_TOO_FEW_DATA_PTS(-165): nSize must not be less than 2

STATS_ERROR_SETTING(-151): nOrder must not be less than 1

STATS_ERROR_SVD_FAIL(-179): The singular value decomposition is failed

STATS_ERROR_RANK_DEFICIENT(-180): The pX is not full rank.

STATS_ERROR_BAD_WEIGHT(-108): Some data of the weight are less than zero

Examples

EX1

void fitpoly_ex1()
{
    vector vX = {1,   2,    3,   4,     5};
    vector vY = {5.5, 43.1, 128, 290.7, 498.4};
    int nOrder = 3;
    vector vCoeff;
    vCoeff.SetSize(nOrder+1);
    fitpoly(vX, vY, nOrder, vCoeff);
    for (int i = 0; i <= nOrder; i++)
        printf("%g\n", vCoeff[i]);
}

EX2

void fitpoly_ex2(Curve& crv)
{
    int nOrder = 3;
    vector vCoeff;
    vCoeff.SetSize(nOrder+1);
    
    vector vError(nOrder+1);
    
    fitpoly(crv, nOrder, vCoeff, vError);
    
    for (int i = 0; i <= nOrder; i++)
    	printf("%d: Coeff = %g, Error = %g\n", i+1, vCoeff[i], vError[i]);
}

void run_fitpoly_ex2()
{
	Worksheet wks = Project.ActiveLayer();
	if( wks && wks.GetNumCols() >= 2 )
	{
		Curve crv(wks, 0, 1);
		fitpoly_ex2( crv );
	}
}

EX3

void fitpoly_ex3(Curve& crv)
{    
    int nOrder = 3;
    vector vCoeffs(nOrder+1);
    
    if( fitpoly(crv, nOrder, vCoeffs))
    {
        for (int i = 0; i <= nOrder; i++)
            printf("%g\n", vCoeffs[i]);
    }
}

void run_fitpoly_ex3()
{
	Worksheet wks = Project.ActiveLayer();
	if( wks && wks.GetNumCols() >= 2 )
	{
		Curve crv(wks, 0, 1);
		fitpoly_ex3( crv );
	}
}

EX4

void fitpoly_ex4()
{
    vector vX = {1,   2,    3,   4,     5};
    vector vY = {5.5, 43.1, 128, 290.7, 498.4};
    int nOrder = 3;
    int nSize = vX.GetSize();
    vector vCoeff;
    vCoeff.SetSize(nOrder+1);
    fitpoly(nOrder, vX, vY, nSize, vCoeff);
    for (int i = 0; i <= nOrder; i++)
        printf("%g\n", vCoeff[i]);
}

Remark

The function used for fitting function parameter initialization.

Fit a polynomial equation to a curve or curve segment and return the parameter coefficients. If specified, only the Nth segment of M equal curve segments is fit.