[FieldTrip] selecting which dimension to average over in ft_singleplotER

[mattmizumi at gmail.com]

A simple newbie question about ft_singleplotER: given a coherence 
spectrum, as follows,

fd =

      labelcmb: {'vStr1'  'vStr2'}
        dimord: 'chan_freq_time'
     cohspctrm: [1x100x101 double]
          freq: [1x100 double]
          time: [1x101 double]
           dof: [1x100 double]
           cfg: [1x1 struct]

how can I plot frequency against coherence? The default behavior of 
ft_singleplotER in this case is to average over frequency:

cfg = [];
cfg.parameter        = 'cohspctrm';
cfg.refchannel       = 'vStr2';
cfg.channel          = 'vStr1';
ft_singleplotER(cfg, fd);

selected 1 channels for cohspctrm
selection cohspctrm along dimension 2
averaging cohspctrm over freq
the call to "ft_singleplotER" took 0 seconds

..but I cannot find a way to get it to average over time instead. How 
can I do this?

(Of course, I know I can plot this manually. But I would like to 
understand how to use the ft plotting functions. I can't find anything 
pertinent in the coherence and plotting tutorials, or the help for 
ft_singleplotER.)

Thanks!

-- Matt