I have this problem (see the picture attached). The baseline is noisy, so I have applied a lowpass filter (1 Hz, y=lowpass(I_P,1,6250). The data looks amazing but the spikes are smaller (of course, because I applied a low-pass filter).
So, in short, I want to apply the same low-pass filter (1Hz) exclusively to the baseline, i.e. from -10 pA to + 50 pA, so that the data baseline is improved signal-wise, and the spike amplitude remains untouchable (keeping the real amplitude).
The signal inside the green box is the data I want to filter. The signal inside the red box is the data I do not want to filter.