Hi gschmied,
Try the Origin C function pasted below which calls NAG library to perform the spline interpolation.
Once you add this function to your workspace and compile, you can then go to the script window and type command such as:
nag_spline data1_b 3000
and a new wks will be generated with the spline values for data_b.
The NAG function also returns error code for very large numbers, but with dataset such as the one you mentioned - data1_a filled with row numbers 1 thru 30 and data1_b = col(a)^(5/3) - I could get the spline curve with 5000 points.
Note that this function assumes the X values of the data are sorted and are in ascending/increasing order.
Easwar
OriginLab.
P.S. I tested this with 7SR4
#include <OC_nag.h> // this contains all the NAG headers,
void nag_spline(string strYDataset, int nPts)
{
// Check nPts
if( nPts < 1 )
{
out_str("Number of points invalid!");
return;
}
// Declare curve using Y dataset name
Curve crvData(strYDataset);
// Create a copy of the curve
Curve crvCopy(crvData);
if( !crvCopy )
{
out_str("Failed to create curve from specified dataset name!");
return;
}
// Copy Y, X values of curve to vectors
vector vecX, vecY;
Dataset dsX;
crvCopy.AttachX(dsX);
vecY = crvCopy;
vecX = dsX;
// Set up vectors for return values from NAG function
vector vecXSpline(nPts), vecYSpline(nPts);
// Fill X vector with nPts that cover the X range of the curve
// Assume X is sorted ascending
double dMin, dMax, dStep;
int nDataSize = vecX.GetSize();
dMin = vecX[0];
dMax = vecX[nDataSize - 1];
dStep = (dMax - dMin) / (nPts - 1);
vecXSpline.Data(dMin, dMax, dStep);
// First compute spline coefficients
Nag_Spline spline;
int iRet;
if( (iRet = nag_1d_spline_interpolant(nDataSize, vecX, vecY, &spline)) != 0 )
{
printf("NAG computation of spline coefficients returned error: %d\n", iRet);
return;
}
// Now compute spline curve at each x point
double fit;
int iS = vecXSpline.GetSize();
for(int ii = 0; ii < iS; ii++)
{
if( (iRet = nag_1d_spline_evaluate(vecXSpline[ii], &fit, &spline)) != 0 )
{
printf("NAG spline computation failed at x = %f with error code: %d\n", vecXSpline[ii], iRet);
return;
}
vecYSpline[ii] = fit;
}
// Succeeded in computing spline - write results to new wks
WorksheetPage wpg;
wpg.Create("Origin");
Worksheet wks = wpg.Layers(0);
while( wks.DeleteCol(0) );
wks.AddCol("SplineX");
wks.Columns(0).SetType(OKDATAOBJ_DESIGNATION_X);
wks.AddCol("SplineY");
string strLabel;
strLabel.Format("NAG Spline Interpolation for %s", strYDataset);
wpg.Label = strLabel;
Dataset dsXSpline(wks, 0);
Dataset dsYSpline(wks, 1);
dsXSpline = vecXSpline;
dsYSpline = vecYSpline;
// Clean up
nag_free(spline.lamda);
nag_free(spline.c);
}
Edited by - easwar on 07/05/2005 11:04:13 AM
B-spline interpolation not smooth?
Posted - 07/05/2005 : 01:21:15 AM
