# [FieldTrip] Question pertaining to frequency resolution for time-frequency analysis

Wijs, C. c.wijs at student.rug.nl
Wed May 12 12:24:31 CEST 2021

```Dear all,

For a uni research project I am trying to perform a TFR analysis on
segmented data. This was not the main aim of my analysis (which are ERP
amplitudes), but me and my supervisor decided that I would have an
(exploratory) look at it. The issue I am facing is that the trials I have
defined (and preprocessed/cleaned) are rather short, ranging from -0.1s
prior to a cue, to 0.6s after a cue, which leaves me with little wiggle
room.

I've decided to follow the method used in section "Time-frequency analysis
I" from the tutorial at :
https://www.fieldtriptoolbox.org/tutorial/timefrequencyanalysis/#time-frequency-analysis-i
. At the end of this section a "warning" is given that one should think
critically about the used frequency resolution. When using a 2Hz frequency
resolution, corresponding to a 500ms time window for the taper,  one
cannot, according to the message, interpret any odd-numbered frequencies. I
do get values for the odd numbered frequencies, but these are
meaningless/incorrect/invalid I assume?

What I would like to do is have a 1Hz frequency resolution, such that I get
(meaningful) values for each integer frequency (within a range of course).
If I understand the type of analysis correctly, this would correspond to a
1s time window for the taper, making the first and last 500ms of my trial
not be included in the output of the analysis. The problem of course, is
that my trials last only 700 ms, from 100ms prior till 600ms post cue, so I
would be left with nothing.

Am I just out of luck, and will I have to do the analysis with a minimal
2Hz frequency resolution? (which already leaves me with quite a short
period of TFR analysis, as this cuts about 250ms from either end of the
trial).

Thank you very much for your time and kind regards,

Chiel Wijs
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