utilities.py 文件源码

def __init__(self, x, y, yp=None):
        npts = len(x)
        mat = np.zeros((3, npts))
        # enforce continuity of 1st derivatives
        mat[1,1:-1] = (x[2:  ]-x[0:-2])/3.
        mat[2,0:-2] = (x[1:-1]-x[0:-2])/6.
        mat[0,2:  ] = (x[2:  ]-x[1:-1])/6.
        bb = np.zeros(npts)
        bb[1:-1] = ((y[2:  ]-y[1:-1])/(x[2:  ]-x[1:-1]) -
                    (y[1:-1]-y[0:-2])/(x[1:-1]-x[0:-2]))
        if yp is None: # natural cubic spline
            mat[1,0] = 1.
            mat[1,-1] = 1.
            bb[0] = 0.
            bb[-1] = 0.
        elif yp == '3d=0':
            mat[1, 0] = -1./(x[1]-x[0])
            mat[0, 1] =  1./(x[1]-x[0])
            mat[1,-1] =  1./(x[-2]-x[-1])
            mat[2,-2] = -1./(x[-2]-x[-1])
            bb[ 0] = 0.
            bb[-1] = 0.
        else:
            mat[1, 0] = -1./3.*(x[1]-x[0])
            mat[0, 1] = -1./6.*(x[1]-x[0])
            mat[2,-2] =  1./6.*(x[-1]-x[-2])
            mat[1,-1] =  1./3.*(x[-1]-x[-2])
            bb[ 0] = yp[0]-1.*(y[ 1]-y[ 0])/(x[ 1]-x[ 0])
            bb[-1] = yp[1]-1.*(y[-1]-y[-2])/(x[-1]-x[-2])
        y2 = solve_banded((1,1), mat, bb)
        self.x, self.y, self.y2 = (x, y, y2)