def characteristics(char, title=''):
    fig, axs = plt.subplots(2, 2, figsize=(10, 8), sharex=True)
    if title:
        fig.suptitle(title)

    n = np.array(char['n'])*60
    pmech = np.array(char['pmech'])*1e-3

    axs[0, 0].plot(n, np.array(char['T']), 'C0-', label='Torque')
    axs[0, 0].set_ylabel("Torque / Nm")
    axs[0, 0].grid()
    axs[0, 0].legend(loc='center left')
    ax1 = axs[0, 0].twinx()
    ax1.plot(n, pmech, 'C1-', label='P mech')
    ax1.set_ylabel("Power / kW")
    ax1.legend(loc='lower center')

    axs[0, 1].plot(n[1:], np.array(char['u1'][1:]), 'C0-', label='Voltage')
    axs[0, 1].set_ylabel("Voltage / V",)
    axs[0, 1].grid()
    axs[0, 1].legend(loc='center left')
    ax2 = axs[0, 1].twinx()
    ax2.plot(n[1:], char['cosphi'][1:], 'C1-', label='Cos Phi')
    ax2.set_ylabel("Cos Phi")
    ax2.legend(loc='lower right')

    if 'id' in char:
        axs[1, 0].plot(n, np.array(char['id']), label='Id')
    if 'iq' in char:
        axs[1, 0].plot(n, np.array(char['iq']), label='Iq')
    axs[1, 0].plot(n, np.array(char['i1']), label='I1')
    axs[1, 0].set_xlabel("Speed / rpm")
    axs[1, 0].set_ylabel("Current / A")
    axs[1, 0].legend(loc='center left')
    if 'beta' in char:
        ax3 = axs[1, 0].twinx()
        ax3.plot(n, char['beta'], 'C3-', label='Beta')
        ax3.set_ylabel("Beta / °")
        ax3.legend(loc='center right')
    axs[1, 0].grid()

    plfe = np.array(char['plfe'])*1e-3
    plcu = np.array(char['plcu'])*1e-3
    pl = np.array(char['losses'])*1e-3
    axs[1, 1].plot(n, plcu, 'C0-', label='Cu Losses')
    axs[1, 1].plot(n, plfe, 'C1-', label='Fe Losses')
    axs[1, 1].set_ylabel("Losses / kW")
    axs[1, 1].legend(loc='center left')
    axs[1, 1].grid()
    axs[1, 1].set_xlabel("Speed / rpm")
    ax4 = axs[1, 1].twinx()
    ax4.plot(n[1:-1], char['eta'][1:-1], 'C3-', label="Eta")
    ax4.legend(loc='upper center')
    ax4.set_ylabel("Efficiency")

    fig.tight_layout()