# Epochs.apply_baseline

Hi everyone,
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

Hello,

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.