I am trying for filters for my experimental data

I am trying to filter the data i have got from my sensor. The graph displayed on the top is the data with noise and after I applied the filter, the top graph turned into something (thepicture at the bottom) which i did not want.The trend shown by the graph on the top is right, but the second plot at the bottom is wrong. I just want to reduce/eliminate the noise (as shown by the peaks) from the plot on the top. I used 4th order buttersworth filter.

Please advice. Thank you in advance

Answer 1

[Star Strider]

My guess is that you used a highpass filter, since it seems that you eliminated the low frequencies and kept the noise. You probably need a lowpass filter instead. If you have R2018a or a later release, use the lowpass (link) function, although these are relatively easy to design using the ellip and related functions. .