glm.py 文件源码

def cosine_kernel(x):
    '''
    Raised cosine basis kernel, normalized such that it integrates to 1
    centered at zero. Time is rescaled so that the kernel spans from
    -2 to 2

    Parameters
    ----------
    x : vector

    Returns
    -------
    vector
        $\\tfrac 1 4 + \\tfrac 1 2 cos(x)$ if $x\in[-\pi,\pi]$, otherwise 0.
    '''
    x = np.float64(np.abs(x))/2.0*np.pi
    return np.piecewise(x,[x<=np.pi],[lambda x:(np.cos(x)+1)/4.0])