def make_qq_plot(kev, obs, mdl, unit, key_text):
    import omega as om
    kev = np.asarray(kev)
    obs = np.asarray(obs)
    mdl = np.asarray(mdl)
    c_obs = np.cumsum(obs)
    c_mdl = np.cumsum(mdl)
    mx = max(c_obs[-1], c_mdl[-1])
    p = om.RectPlot()
    p.addXY([0, mx], [0, mx], '1:1')
    p.addXY(c_mdl, c_obs, key_text)
    locs = np.array([0, 0.05, 0.08, 0.11, 0.17, 0.3, 0.4, 0.7, 1]) * (kev.size - 2)
    c0 = mx * 1.05
    c1 = mx * 1.1
    for loc in locs:
        i0 = int(np.floor(loc))
        frac = loc - i0
        kevval = (1 - frac) * kev[i0] + frac * kev[i0+1]
        mdlval = (1 - frac) * c_mdl[i0] + frac * c_mdl[i0+1]
        obsval = (1 - frac) * c_obs[i0] + frac * c_obs[i0+1]
        p.addXY([mdlval, mdlval], [c0, c1], '%.2f keV' % kevval, dsn=2)
        p.addXY([c0, c1], [obsval, obsval], None, dsn=2)
    p.setLabels('Cumulative model ' + unit, 'Cumulative data ' + unit)
    p.defaultKeyOverlay.vAlign = 0.3
    return p