// This function assumes a graph layer is active.
// It then takes the last data plot in the layer and clips all other 
// data from other data plots that are to the left of this clipping dataset.
// The clipping is done by setting y values to missing value.
void clip_left()
{
	// Assume graph layer is active
	GraphLayer gly = Project.ActiveLayer();
	if( !gly ) return;

	// Count number of data plots in layer
	int nDataPlots = 0;
	foreach(DataPlot dp in gly.DataPlots)
	{
		nDataPlots++;
	}
	// If less than two datasets, quit
	if( nDataPlots < 2 ) return;
	
	// Assume last data plot is the one used for clipping
	// Declare curve and attach to last data plot
	Curve crvClip(gly.DataPlots(nDataPlots - 1));
	int nClipDataSize = crvClip.GetSize();
	// Get X values
	vector vecClipX;
	get_x_values(crvClip, vecClipX);

	// Loop over all data plots other than the last one
	for(int idp = 0; idp < nDataPlots - 1; idp++)
	{
		Curve crvData(gly.DataPlots(idp));
		// Loop over all adjacent x value pairs in clip dataset
		double x1, x2, y1, y2, cy1, cy2;
		for(int i = 0; i < nClipDataSize - 1; i++)
		{
			// Get x,y of clip data curve
			x1 = vecClipX[i];
			x2 = vecClipX[i + 1];
			cy1 = Curve_yfromX(&crvClip, x1);
			cy2 = Curve_yfromX(&crvClip, x2);
			// Get y of current data curve and check for intersection
			y1 = Curve_yfromX(&crvData, x1);
			y2 = Curve_yfromX(&crvData, x2);
			if( (cy1 - y1) * (cy2 - y2) < 1 )
			{
				// The two curves intersect - find intersection point x value
				double m1, m2, c1, c2;
				m1 = (cy2 - cy1) / (x2 - x1);
				c1 = (cy1 * x2 - cy2 * x1 ) / (x2 - x1);
				m2 = (y2 - y1) / (x2 - x1);
				c2 = (y1 * x2 - y2 * x1 ) / (x2 - x1);
				double xint = (c2 - c1) / (m1 - m2); 
				// Set points to left of this x value as missing				
				set_left_missing(crvData, xint);
				break;
			}
		}
	}	
}
	
// This function sets points to left as missing values
static void set_left_missing(Curve& crv, double dx)
{
	// Get X values of curve into vector
	vector vecX;
	get_x_values(crv, vecX);
	int nSize = crv.GetSize();
	// Loop over all points in data curve
	for(int i = 0; i < nSize; i++)
	{
		// If current x is less than cutoff x, set y as missing
		if( vecX[i] < dx )
			crv[i] = NANUM;
		else
			break;
	}
}

// This function fills vector with X values of the curve
static void get_x_values(Curve& crvClip, vector& vecClipX)
{
	if( crvClip.HasX() )
	{
		Dataset dsX;
		crvClip.AttachX(dsX);
		vecClipX = dsX;
	}
	else
	{
		vecClipX.Data(1, crvClip.GetSize(), 1)
	}
}
//