Plot welch PSD with peaks as scatter points

    Args
    ----
    f: ndarray
        Array of frequencies produced with PSD
    S: ndarray
        Array of powers produced with PSD
    peak_loc: ndarray
        Indices of peak locations in signal
    title: str
        Main title for plot

def plot_welch_peaks(f, S, peak_loc=None, title=''):
    '''Plot welch PSD with peaks as scatter points

    Args
    ----
    f: ndarray
        Array of frequencies produced with PSD
    S: ndarray
        Array of powers produced with PSD
    peak_loc: ndarray
        Indices of peak locations in signal
    title: str
        Main title for plot
    '''
    plt.plot(f, S, linewidth=_linewidth)
    plt.title(title)
    plt.xlabel('Fequency (Hz)')
    plt.ylabel('"Power" (g**2 Hz**−1)')

    if peak_loc is not None:
        plt.scatter(f[peak_loc], S[peak_loc], label='peaks')
        plt.legend(loc='upper right')

    plt.show()

    return None