21+1 points for a ruddy duck Cubic Spline Interpolation line1=X, line2=Y
 0.9  1.3  1.9  2.1  2.6  3.0  3.9  4.4  4.7  5.0  6.0  7.0  8.0  9.2 10.5 11.3  11.6  12.0  12.6  13.0  13.3  13.9
 1.3  1.5  1.85 2.1  2.6  2.7  2.4  2.15 2.05 2.1 2.25 2.3  2.25 1.95  1.4  0.9  0.7  0.6    0.5   0.4   0.25  0.37