I havent had much experience with low pass filters but,I do understand what they do. I was implementing one on an AC signal above. This is a sampled input, and I dont see how would you call the picture an implementation of a LPF. From what I thought, frequency is on the horizontal scale , so if the gap between 2 samples/lines was less than a threshold/cutoff, then it would not be taken into account. But I dont see how the height of the sample is reduced by an LPF?
Also, Why do you get varying heights, and not just a straight line, so an AC wave with a DC part on top?