[Java]Lowpass Filter(Linear weight version)

LinearWeightLowpassFilter.java

/**
 * Copyright 2006-2016 Tom Misawa(riversun.org@gmail.com)
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 http://www.apache.org/licenses/LICENSE-2.0
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
package org.riversun;

/**
 * Linear weight lowpass filter
 * 
 * @author Tom Misawa (riversun.org@gmail.com)
 * 
 */
public class LinearWeightLowpassFilter {

	public static void main(String[] args) {

		// example

		final float[] data = new float[] { 100f, 100f, 200f, 200f };
		final int sampleRange = 20;

		LinearWeightLowpassFilter filter = new LinearWeightLowpassFilter();
		filter.setSamplingRange(sampleRange);

		for (int i = 0; i < data.length; i++) {

			filter.putValue(data[i]);

			System.out.println(data[i] + " added. current filtered val is " + filter.getFilteredValue());
		}
	}

	private int mSamplingRange;
	private float[] mSamplingBuffer;
	private float mCurrentFilterVal;
	private int mCurrentDataNumber = 0;

	public LinearWeightLowpassFilter() {
		setSamplingRange(20);
	}

	public void setSamplingRange(int range) {
		mSamplingRange = range;
		mSamplingBuffer = new float[mSamplingRange];
	}

	/**
	 * Get the latest filtered(linear weighted) value
	 * 
	 * @return
	 */
	public float getFilteredValue() {
		float filteredVal = mCurrentFilterVal;
		return filteredVal;
	}

	/**
	 * Put the current value to filter
	 * 
	 * @param val
	 */
	public void putValue(float val) {
		mCurrentFilterVal = filter(val, mSamplingBuffer);
	}

	public float[] getSampingBuffer() {
		return mSamplingBuffer;
	}

	public int getSamplingRange() {
		return mSamplingRange;
	}

	public void fillValue(float val) {
		for (int i = 0; i < mSamplingBuffer.length; i++) {
			mSamplingBuffer[i] = val;
		}
	}

	private float filter(float inputValue, float[] samplingBuffer) {

		mCurrentDataNumber++;
		int range = samplingBuffer.length;
		if (mCurrentDataNumber < range) {
			range = mCurrentDataNumber;
		}

		for (int i = (range - 1) - 1; i >= 0; i--) {
			// copy next element to prev element
			samplingBuffer[i + 1] = samplingBuffer[i];
		}

		// Add current value to last
		samplingBuffer[0] = inputValue;

		float numerator = 0;

		float denominator = 0;

		for (int n = 0; n < range; n++) {

			// weight linearly
			numerator += (range - n) * samplingBuffer[n];
			denominator += (range - n);
		}

		final float currentOutputVal = numerator / denominator;

		return currentOutputVal;

	}

}