[FieldTrip] using ft_megplanar with sinle-trial TFRs

[Frédéric Roux]

Dear all,

my question relates to the computation of combined planar gradients
using the ft_combineplanar function.

Our data has been recorded with an Elekta Neuromag 306 channel system,
and I would like to know if it is "safe" to compute combined gradients
before calling ft_freqstatistics, if the input data contains single trial TFRs.

The reason why I am asking is because in the documentation of the function it  says
% Use as
% [data] = ft_combineplanar(cfg, data)
% where data contains an averaged planar gradient (either ERF or TFR).

However, the following tutorial suggests that this can be safely applied if
the input data contains TFRs which have been computed with the cfg.keeptrials = 'yes' option:
http://fieldtrip.fcdonders.nl/tutorial/cluster_permutation_freq

I am bit confused as both information (the fieldtrip documentation and the tutorial)
seem to contradict each other.

The 2 options that are see are:

1) compute TFRs with cfg.keeptrials = 'yes', then call ft_frestatistics, then call ft_combineplanar 
   by using the output of ft_freqstatistics as input for the ft_combineplanar function.
2) compute TFRs with cfg.keeptrials = 'yes', then call ft_combineplanar, then call ft_freqstatistics

Could anyone with experience on this issue please let me know what the best way
to proceed would be?

Fred
---------------------------------------------------------------------------