Evaluate a piecewise polynomial (spline)

User Questions
, ,
3

Hi Jonathan,

CasADi implements its own splines

If I use CasADi splines I have the same problem as with ppval(…). The position where I evaluate the spline is an optimization variable (SX.sym). For example using the following lines of code

x = -1 : 0.1 : 1;
y = randn(size(x));

% state variable of dynamics equation
x_eval = SX.sym('x_eval'); 

pp_casadi = casadi.interpolant('pp', 'bspline', {x}, y);

% meaningless cost function just for demonstration
expr_ext_cost = pp_casadi(x_eval)^2;

results in the following error during code generation:

Error using casadi.Function/call (line 935)
.../casadi/core/function_internal.cpp:1821: 'eval_sx' not defined for BSplineInterpolant

Error in casadi.Function/paren (line 1763)
        res = self.call(varargin);

Error in casadi.Function/subsref (line 1744)
        [varargout{1:nargout}]= paren(self, s.subs{:});

Error in acadosNLPFormulation (line 46)
    expr_ext_cost = pp_casadi(x_eval)^2;

BR
Martin