`Vojtech Pavlik <vojtech@suse.cz> writes:> Btw, what I don't completely understand is why you need linear> regression, when you're not trying to detect motion or something like> that. Basic floating average, or even simpler filtering like the input> core uses for fuzz could work well enough I believe.Indeed, this function doesn't make much sense:+static inline int smooth_history(int x0, int x1, int x2, int x3)+{+	return x0 - ( x0 * 3 + x1 - x2 - x3 * 3 ) / 10;+}In the X driver, a derivative estimate is computed from the last 4absolute positions, and in that case the least squares estimate isgiven by the factors [.3 .1 -.1 -.3]. However, in this case you wantto compute an absolute position estimate from the last 4 absolutepositions, and in this case the least squares estimate is given by thefactors [.25 .25 .25 .25], ie a floating average. If the function ischanged to this:+static inline int smooth_history(int x0, int x1, int x2, int x3)+{+	return (x0 + x1 + x2 + x3) / 4;+}the standard deviation of the noise will be reduced by a factor of 2compared to the unfiltered values. With the old smooth_history()function, the noise reduction will only be a factor of 1.29.-- Peter Osterlund - petero2@telia.comhttp://web.telia.com/~u89404340-To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.kernel.orgMore majordomo info at  http://vger.kernel.org/majordomo-info.htmlPlease read the FAQ at  http://www.tux.org/lkml/`