sandbox/hugoj/test_interp/interpolate.h

    #ifndef INTERPOLATE_H
    #define INTERPOLATE_H
    
    double PI;
    void cart2pol(double x, double y, double *rho, double *phi);
    void pol2cart(double rho, double phi, double *x, double *y);
    double interp_lin(double x[], double y[], int Nx, int Ny, double xi, double yi, double F[]);
    
    #endif