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faq:why_does_my_tfr_look_strange [2013/01/07 22:40]
ingrid [Why does my TFR look strange (part I, demeaning)?]
faq:why_does_my_tfr_look_strange [2017/08/17 11:21] (current)
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 == cfg.polyremoval == == cfg.polyremoval ==
-**Note,** in the above code cfg.polyremoval = -1. This option has been introduced in July 2011 (see [[http://​mailman.science.ru.nl/​pipermail/​fieldtrip/​2012-January/​004666.html|this email thread]]. The default behavior is cfg.polyremoval = 0, which means that zero-order polynomial is removed, which just means demeaning ​takes place. So if you're just using the default in ft_preprocessing, your data will be automatically demeaned (you don't have to do in separately in ft_preprocessing),​ aiming to avoid these surprising effects. A value of -1 is NOT the default behavior, because it will lead to no demeaning whatsoever, and therefore shows the strange behavior. Also see [[faq:​why_does_my_tfr_look_strange_part_ii|Why does my TFR look strange (part II)?]] for info on detrending.+**Note,** in the above code cfg.polyremoval = -1. This option has been introduced in July 2011 (see [[http://​mailman.science.ru.nl/​pipermail/​fieldtrip/​2012-January/​004666.html|this email thread]]). The default behavior is cfg.polyremoval = 0, which means that the zero-order polynomial is removed, which is equal to demeaning. So if you're just using the default in ft_freqanalysis, your data will be automatically demeaned (you don't have to do in separately in ft_preprocessing),​ aiming to avoid these surprising effects. A value of -1 is NOT the default behavior, because it will lead to no demeaning whatsoever, and therefore shows the strange behavior. Also see [[faq:​why_does_my_tfr_look_strange_part_ii|Why does my TFR look strange (part II)?]] for info on detrending ​(is first-order polynomial removal).