/*
 * #%L
 * ImgLib2: a general-purpose, multidimensional image processing library.
 * %%
 * Copyright (C) 2009 - 2013 Stephan Preibisch, Tobias Pietzsch, Barry DeZonia,
 * Stephan Saalfeld, Albert Cardona, Curtis Rueden, Christian Dietz, Jean-Yves
 * Tinevez, Johannes Schindelin, Lee Kamentsky, Larry Lindsey, Grant Harris,
 * Mark Hiner, Aivar Grislis, Martin Horn, Nick Perry, Michael Zinsmaier,
 * Steffen Jaensch, Jan Funke, Mark Longair, and Dimiter Prodanov.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
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 *    and/or other materials provided with the distribution.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 */

package net.imglib2.meta.axis;

import java.util.HashMap;
import java.util.Set;

import net.imglib2.meta.AbstractCalibratedAxis;
import net.imglib2.meta.AxisType;
import net.imglib2.meta.CalibratedAxis;

/**
 * An {@link CalibratedAxis} whose calibration is defined by an equation with
 * one or more variables.
 * 
 * @author Curtis Rueden
 */
public abstract class VariableAxis extends AbstractCalibratedAxis {

	private HashMap<String, Double> vars = new HashMap<String, Double>();

	// -- Constructors --

	public VariableAxis(final AxisType type) {
		super(type);
	}

	public VariableAxis(final AxisType type, final String unit) {
		super(type, unit);
	}

	// -- VariableAxis methods --

	public Double get(final String name) {
		return vars.get(name);
	}

	public void set(final String name, final Double value) {
		if (value == null) vars.remove(name);
		else vars.put(name, value);
	}

	public int numVars() {
		return vars.size();
	}

	public Set<String> vars() {
		return vars.keySet();
	}

}

Add VariableAxis base class to unify things