def plot_xft(fignum, XF, T, e, b):
    """ function to plot series of chi measurements as a function of temperature, holding field constant and varying frequency
    """
    plt.figure(num=fignum)
    plt.clf()
    if not isServer:
        plt.figtext(.02, .01, version_num)
    plt.xlabel('Frequency (Hz)')
    plt.ylabel('Susceptibility (m^3/kg)')
    k = 0
    F, X = [], []
    for xf in XF:
        X.append(xf[0])
        F.append(xf[1])
    plt.plot(F, X)
    plt.semilogx()
    plt.title(e + ': B = ' + '%8.1e' % (b) + ' T')

    plt.legend(['%i' % (int(T)) + ' K'])