circleby2ptsradius.py 文件源码

def circleby2ptsradius(pt1Vec, pt2Vec, radius):

    if radius < la.norm(pt1Vec-pt2Vec)/2:
        centerVec1 = np.array(['NaN', 'NaN'])
        centerVec2 = np.array(['NaN', 'NaN'])
    else:
        a = pt1Vec[0]**2-pt2Vec[0]**2
        b = pt1Vec[1]**2-pt2Vec[1]**2
        c = -2*(pt1Vec[0]-pt2Vec[0])
        d = -2*(pt1Vec[1]-pt2Vec[1])
        e = a+b
        Coeff1 = 1+(d/c)**2
        Coeff2 = ((2*d*e/c**2) +(pt2Vec[0]*2*d/c) -2*pt2Vec[1])
        Coeff3 = ((e/c)**2+(2*pt2Vec[0]*e/c)+pt2Vec[0]**2+pt2Vec[1]**2-\
            radius**2)

        All_coeff = np.array([Coeff1, Coeff2, Coeff3])
        Eq_root = np.roots(All_coeff)

        # centersArray--center of the circle. It is a 2x2 matrix. First row
        # represents first possible center (x1, y1) and second row is the 
        # second possible center.
        centersArray = np.zeros((len(Eq_root),2))

        for i in list(range(len(Eq_root))):
            x = -(e+d*Eq_root[i])/c
            centersArray[i,0] = x
            centersArray[i,1] = Eq_root[i]

        # Check if values in centerArray are real or unreal numbers
        if la.norm(centersArray.imag) != 0:
            print('Circle with the specified radius does not pass through',
                'specified points', sep=" ")
            centerVec1 = np.array(['NaN', 'NaN'])
            centerVec2 = np.array(['NaN', 'NaN'])
        else:
            centerVec1 = centersArray[0, :]
            centerVec2 = centersArray[1, :]

    return centerVec1, centerVec2