Say I have an array representing a signal, going from 30 to -30 in 1000 increments, with a little bit of noise on those values. If I apply any king of low pass filtering (Besset, Butterworth, Savitsky-Golay, etc), then the 1st point is now very near zero and the next few points reach progressively for +30 after some wild oscillations depending on the filter and its parameters.
It's been a while (ahem, decades) since I last delved into the maths of DSP, so I'm a bit rusty and looking to know what I should do about it. I thought that the solution was to window my data before filtering it, but it doesn't seem to change much.
Obviously what I want to end up with is a nice 30 to -30 ramp, with the noise removed.