org.usfirst.frc.team1736.lib.SignalMath

Class MedianFilter

java.lang.Object

org.usfirst.frc.team1736.lib.SignalMath.MedianFilter

public class MedianFilter
extends java.lang.Object

Class which defines a simple median filter. After initialization, the "filter()" method can simply be called with the newest input, and the most recent filtered output will be returned. Median filters are useful for rejecting noise which induces large errors for single loops ( "shot noise")

Constructor Summary

Constructors

Constructor and Description
MedianFilter(int length, double init_val) Initialize all things needed for the median filter.

Method Summary

Modifier and Type	Method and Description
double	filter(double input) Add a new input to the filter and get the current output from the filter

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MedianFilter

public MedianFilter(int length,
                    double init_val)

Initialize all things needed for the median filter.

Parameters:

length - Number of previous values to consider for the median calculation. 5 is probably a good starting point. Bigger length means more noise rejection, but also induces more delay from input to output. Also, median calculations are non-linear in big-O time complexity, so cranking this number up will really start to slow things down.

init_val - Initial output of the filter. Usually zero, unless you know something about your system that we don't.

Method Detail

filter

public double filter(double input)

Add a new input to the filter and get the current output from the filter

Parameters:

input - - new value to add to the filter

Returns:

the present output filtered value