[FieldTrip] Excluding a subject

Stephen Whitmarsh stephen.whitmarsh at gmail.com
Thu May 10 13:07:17 CEST 2012

Hi Tony,

Thanks for your question.

First of all, I do not fully understand what you mean with 'without
computing the averages again', but I'll have a shot at it.

In ft_freq/timelock-statistics you enter all your 'units of
observations', i.e. data structures per subject or condition that you
want to compare, together with the design matrix. The designmatrix is
a one or two row matrix with as many columns as your have
data-entries. One of the rows codes the group/condition membership of
those entries (the independent variable). They can be subjects (group
analysis) or trials (within-subjects analysis). Another row might be
used to code the observation number in case you are doing a paired

To exclude one data entry (i.e. subject) for your
ft_timelockstatistics you could either:
1) not enter that datastructure as data in ft_freqstatistics, and also
remove it from your design matrix.
2) keep your input to ft_timelockstatistics the same but use a zero
for that entry in you design matrix. In this case that data input will
not be used to calculate your statistics.

I would say the second option is more elegant, but it is more prone to
mistakes perhaps. You would do me a favour if you would doublecheck
that it gives you the same results as option 1.

I hope this answers your question,


On 10 May 2012 12:09, Roni Tibon <ronitibon at gmail.com> wrote:
> Hi all,
> Is there an elegant way to exclude a subject from the statistical analysis
> when using ft_timelockstatistics, without computing the averages again while
> excluding the subject?
> Thanks!
> Roni
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