Bspline boundary type for parametric curve

Question

I want to impose conditions on the derivative at the boundaries for a parametric Bspline.

r=[1.08,1.08,  0.987, 0.82,  0.734, 0.692, 0.40]
phi=np.linspace(0,np.pi/2,len(r))
x, y = r*np.cos(phi), r*np.sin(phi) 
l, r = [(1, 0)], [(1, 0)]    
spl = make_interp_spline(phi, np.c_[x, y], bc_type=(l,r))

I got a ValueError: "cannot reshape array of size 1 into shape (2)" related to rhs[:nleft] = deriv_l_vals.reshape(-1, extradim)

I suspect I imposed the BCs in a wrong way. But when reading the documentation, I only see this way to impose BCs (for a spline in cartesian coordinates). No explicit mention of how to do this in a parametric curve.

Anyone knows how to sort it out? I would avoid to re-write all in a non-parametric form....

Answer 1

Self-answer: as suspected, BCs imposed in the wrong way: obviously, two components needed... e.g.

l, r = [(1, (0,-1))], [(1, (1,0))]