def percentile_at(table, x, axis=1, freq_count=10, interval=10, delta_between_group=0.01):
    C = np.cumsum(table, axis=axis)
    N = np.sum(table, axis=axis)
    P = x * N  # cumulative freq of x

    compare = C > np.tile(P, (freq_count, 1)).T

    index = freq_count - np.sum(compare, axis=axis)  # index of groups that x on
    I = range(index.shape[0])

    L = interval * index + delta_between_group/2
    CF = C.values[I, index-1]

    return L + interval * ((P - CF) / table.values[I, index])