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<font size="4" class="">Dear Sarah,</font>
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<div class=""><font size="4" class="">Thanks for clarifying your question. Now, could you provide the readership with some additional information about how you constructed these data structures, and how you tried to combine them, otherwise we (i.e. the people
who’d want to think along with you to fix your problem) don’t know where to start.</font></div>
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<div class=""><font size="4" class="">Jan-Mathijs</font></div>
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<div class="">On 14 May 2020, at 09:32, Sarah Kirchler <<a href="mailto:sarah.kirchler@gmail.com" class="">sarah.kirchler@gmail.com</a>> wrote:</div>
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<div class="">Dear Jan-Mathijs,</div>
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<div class="">thank you for your answer. I see, i expressed myself not very clear.
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<div class="">I'd like to make the Grand mean for the difference and the sum between two specific frequencies I measured visually wih a SSVEP.
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<div class="">I'd like to do this because I'm interested in how the frequencies are processed in the brain regarding each other and a control measurement.<br class="">
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<div class="">I'm not sure if I can make the difference already when I make the GM or later, when I plot the topography.
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<div class="">I tried to make this by building a datastructure that contains the GM of the one and the other frequency and then usw ft_math to compare them. But this doesn't work for me.
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<div class="">Maybe thats enough information for you to understand the problem better, I'm a beginner so I often explain my problems a little bit confusing, sorry for that.
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<div class="">Best, <br class="">
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<div class="">Sarah<br class="">
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<div dir="ltr" class="gmail_attr">Am Mi., 13. Mai 2020 um 15:30 Uhr schrieb Schoffelen, J.M. (Jan Mathijs) <<a href="mailto:jan.schoffelen@donders.ru.nl" class="">jan.schoffelen@donders.ru.nl</a>>:<br class="">
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<div style="overflow-wrap: break-word;" class=""><font style="" size="4" class="">Dear Sarah,</font>
<div style="" class=""><font size="4" class=""><br class="">
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<div style="" class=""><font size="4" class="">It is not clear what error message you get, nor why you think you should ft_timelockanalysis/ft_timelockgrandaverage/ft_topoplotER.</font></div>
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<div style="" class=""><font size="4" class="">Some pointers: </font></div>
<div style="" class=""><font size="4" class="">-For a mathematical operation to be applied to numeric data that resides within a fieldtrip-style data structure you’d use ft_math.</font></div>
<div style="" class=""><font size="4" class="">-What you want to do (i.e. adding or subtracting estimates of frequency specific power estimated for different frequency bins) probably requires some manual intervention with the data, because FT will likely prevent
you to do so, since it checks whether the frequency bins for the to-be-combined data structures match. I could type some recipe now, but since you are not too clear on the details so I’d rather not spend time on that now. Also, I’d like to give other people
the opportunity to chime in here :).</font></div>
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<div style="" class=""><font size="4" class="">Best wishes,</font></div>
<div style="" class=""><font size="4" class="">Jan-Mathijs</font></div>
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<div class="">On 11 May 2020, at 16:43, <a href="mailto:sarah.kirchler@gmail.com" target="_blank" class="">
sarah.kirchler@gmail.com</a> wrote:</div>
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Dear Fieldtrip Users,<span class=""> </span><br class="">
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thank you for all the help you’ve given me already.<span class=""> </span><br class="">
Now I am trying to make the sum and the difference of the Grand mean from/between two frequencies I measured with an EEG.<span class=""> </span><br class="">
I read that it is possible to make a datastructure using {} within ft_timelockbaseline and then use the option cfg.operation(x1-x2 and so on) as a operation of function ft_topoplotER to make this sum/these differences.<span class=""> </span><br class="">
Now my Problem is that I don’t need to make the baselinecorrection via ft_timelockbaseline because I don’t have the baseline in the datasegment I’m interested in. So I tried to build the datastructure for cfg.operation within ft_timelockanalysis but Fieldtrip
doesn’t allow this and I get an error message.<span class=""> </span><br class="">
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My questions are now:<span class=""> </span><br class="">
1. Can I make the difference also within the ft_timelockgrandavverage function or do I have to make the difference lawer in ft_topoplotER?<span class=""> </span><br class="">
2. If so, how can I or form a datastructure I can use in cfg.operation or make the difference differently with some other function?<br class="">
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I hope you understand me,<span class=""> </span><br class="">
to all you extraordinary brains: thank you in advance,<span class=""> </span><br class="">
<br class="">
Sarah</div>
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