kernels.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
    ----------

    Returns
    -------
    '''
    x = np.float64(np.abs(x))/2.0*pi
    return np.piecewise(x,[x<=pi],[lambda x:(np.cos(x)+1)/4.0])