2.1.18.19 ocmath_tps_fit

Description

This function perform 2D interpolation using thin plate spline method.

Syntax

int ocmath_tps_fit(int nNode, const double *x, const double *y, const double *z, double dSmooth, ocmath_strTPS *strTPS, double* dRegularization)

Parameters

nNode

[input] the number of scatters.

x

[input] the position and the x-coordinates of each points.

y

[input] the position and the y-coordinates of each points.

z

[input] the position and the z-coordinates of each points.

dSmooth

[input] the smooth factor.

strTPS

[output] contains the interpolation coefficients of the fitting.

dRegularization

[output] the regularization factor defined by the value of dsmooth.

Return

OE_NOERROR for successful or

OE_INVALID_POINT Not enough points (n<3) or all the points are colinear;

OE_NULL_POINTER if pointer is null.

OE_INVALID_SMOOTH Parameter dSmooth should not be less than zero.

Examples

EX1

#include <wks2mat.h>
int ocmath_tps_fit_ex1()
{
	// tabulated data on a 3x3 regular grid, points of form (x,y,f(x,y))
	const int iQuantity = 9;
	double afX[] = {0.0, 0.5, 1.0,0.0, 0.5, 1.0,0.0, 0.5, 1.0};
	double afY[] = {0.0, 0.0, 0.0,0.5, 0.5, 0.5,1.0, 1.0, 1.0};
	double afF[] = {1.0, 2.0, 3.0,3.0, 2.0, 1.0,1.0, 2.0, 3.0};
	
	// resample on a 7x7 regular grid
	const int iResample = 6;
	const double fInv = 1.0/(double)iResample;
	int i, j;
	
	// no smoothing, exact interpolation at grid points
	ocmath_strTPS strTPS;
	ocmath_tps_initial(&strTPS);
	
	double dSmooth = 0.1;
	double dReg;
	
	int nRe = ocmath_tps_fit(iQuantity, afX, afY, afF, 
					dSmooth, &strTPS, &dReg);
	
	if(nRe)
	{
		printf("intp error  %d\n", nRe);
		return -1;
	}
	else
	{
		printf("The regularization parameter is %g\n\n",dReg);
	}
	
	// Output the results
	printf( "smooth parameter is %g\n", dSmooth);
	double x, y, z;
	for (j = 0; j <= iResample; j++)
	{
		y = fInv*j;
		for (i = 0; i <= iResample; i++)
		{
			x = fInv*i;
			ocmath_tps_eval(1, &x, &y, &z, &strTPS);
			printf("%9.6f\t", z);
		}
		printf("\n");
	}
	
	ocmath_tps_free(&strTPS);
	return 0;
}

EX2

// This example demonstrates the usage of thin plate spline fitting and XY gridding.
// To test, create an Origin workshhet with three columns that contain XYZ scatters.
// The result will be stored in a newly created Origin matrix window.
#include <wks2mat.h>
void ocmath_tps_fit_ex2()
{
	int nRows = 100;
	int nCols = 100;
	
	Worksheet wks = Project.ActiveLayer();
	wks.SetSize(-1, 3);
	Dataset dsX(wks, 0), dsY(wks, 1), dsZ(wks, 2);
	
	vector vXsrc(dsX), vYsrc(dsY), vZsrc(dsZ);
	vector vXdest(nRows * nCols), vYdest(nRows * nCols), vZdest(nRows * nCols);
	
	int nSize = vXsrc.GetSize();
	
	double dXmin, dXmax, dYmin, dYmax;
	vXsrc.GetMinMax(dXmin, dXmax);
	vYsrc.GetMinMax(dYmin, dYmax);
	
	MatrixLayer ml;
	ml.Create();
	MatrixObject mo = ml.MatrixObjects(0);
	
	mo.SetNumRows(nRows);
	mo.SetNumCols(nCols);
	mo.SetXY(dXmin, dYmin, dXmax, dYmax);
	
	Matrix& mat = mo.GetDataObject();
	
	ocmath_strTPS strTPS;
	ocmath_tps_initial(&strTPS);
	
	double dSmooth = 0.0; // no smoothing, exact interpolation at grid points
	double dReg;
	
	int iRet;
	// Initialization
	iRet = ocmath_tps_fit(nSize, vXsrc, vYsrc, vZsrc, dSmooth, &strTPS, &dReg);
	
	if(iRet) {
		printf("intp error  %d\n", iRet);
		return;
	}
	
	// Create XY gridding.
	iRet = ocmath_mat_to_regular_xyz(NULL, nRows, nCols, dXmin, dXmax, dYmin, dYmax, vXdest, vYdest, NULL);
	
	if (iRet <= 0) { 
		printf("Failed to create XY gridding!\n");
		return;
	}
	
	// Interpolation
	ocmath_tps_eval(nRows * nCols, vXdest, vYdest, mat, &strTPS);
	
	ocmath_tps_free(&strTPS);
}

Remark

See Also

ocmath_tps_eval

Header to Include

wks2mat.h

Reference