void fill_missing()
{
	// Map active layer to a matrix layer object
	MatrixLayer matly = Project.ActiveLayer();
	// If object not valid, then what is active is not a matrix
	if(!matly)
	{
		printf("Active layer is not a matrix!\n");
		return;
	}
	// Create Matrix object and attach to this layer
	Matrix mat;
	mat.Attach(matly);

	// Get number of rows and cols in matrix
	int iNumRows, iNumCols;
	iNumRows = mat.GetNumRows();
	iNumCols = mat.GetNumCols();
	// If less than 2 cols, just quit
	if(iNumCols < 2)
	{
		printf("Too few columns!\n");
		return;
	}
	
	// Loop over all rows to find missing values and then fill them
	for(int iRow = 0; iRow < iNumRows; iRow++)
	{
		bool bFoundGap = false;
		bool bFoundNumber = false;
		int iGapLo, iGapHi;
		// Loop over all columns of the current row
		for(int iCol = 0; iCol < iNumCols; iCol++)
		{
			// Look for the first number - this is to ignore missing values "outside"
			if(mat[iRow][iCol] != NANUM)
			{			
				bFoundNumber = true;
			}
			
			// If number was found, and next cell is missing value, it is start of a gap
			if(bFoundNumber && (NANUM == mat[iRow][iCol]))
			{
				iGapLo = iCol;	
				bFoundGap = true;
				bFoundNumber = false;
			}
			
			// If in gap and next value is number, then that means end of gap - so need to fill
			if(bFoundGap && bFoundNumber)
			{
				iGapHi = iCol - 1;
				bFoundGap = false;
				
				// Fill half of the gap with number from left, and other half with number from right
				int iGapLength = iGapHi - iGapLo + 1;
				if(iGapLength > 1)
				{
					for(int ii = iGapLo; ii < iGapLo + iGapLength / 2; ii++)
						mat[iRow][ii] = mat[iRow][iGapLo - 1];
					for(ii = iGapLo + iGapLength / 2; ii <= iGapHi; ii++)
						mat[iRow][ii] = mat[iRow][iGapHi + 1];
				}
				else
					mat[iRow][iGapLo] = mat[iRow][iGapHi + 1];
			}
		}
	}
}