I am confused and troubled by the function of epochs.apply_baselines. After I used this function, the plot evoked data of the baseline time interval is still fluctuated large. How can I average and smooth the baseline time interval data.
Here is my code and the timeline of my experiment: the first stimulus was presented at the timepoint of 0.3, so the baseline is (-0.05, 0.3);
Hi @mengjin123 -
.apply_baseline() does not smooth the signal - it only removes the average values from the baseline period from each data sample. This is equivalent to moving the signal along the y axis by some value. To remove unwanted frequency content you may want to use filtering. But make sure that you have enough trials per condition to observe nice ERPs
like @mmagnuski said, applying baseline correction merely, for each channel:
- calculates the average amplitude in the baseline period, and
- subtracts this average from the entire epoch.
If there are large amplitude fluctuations during the baseline period, these will still be visible after baseline correction – only the baseline signal will now be centered around zero.