nagcpp::interp::dim1_spline Example
              Knot          B-spline coeff
   i       lambda_{i+2}          N_i(x)
------------------------------------------
   0                             1.0000
   1         0.0000              1.1336
   2         0.4000              1.3726
   3         0.6000              1.7827
   4         0.7500              2.1744
   5         1.0000              2.4918
   6         1.0000              2.7183