/*
 * This file is part of ELKI:
 * Environment for Developing KDD-Applications Supported by Index-Structures
 *
 * Copyright (C) 2022
 * ELKI Development Team
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package elki.utilities.scaling;

/**
 * Interface for scaling functions used, e.g., by outlier evaluation such as
 * Histograms and visualization.
 * <p>
 * When using outlier scaling functions, make sure to invoke
 * {@link elki.utilities.scaling.outlier.OutlierScaling#prepare
 * prepare} to invoke the preprocessing step!
 * <p>
 * Outside of an outlier context, you probably want to use
 * {@link StaticScalingFunction} instead, which may not require a
 * {@code prepare} statement.
 *
 * @author Erich Schubert
 * @since 0.3
 */
public interface ScalingFunction {
  /**
   * Transform a given value using the scaling function.
   *
   * @param value Original value
   * @return Scaled value
   */
  double getScaled(double value);

  /**
   * Get minimum resulting value. May be {@link Double#NaN} or
   * {@link Double#NEGATIVE_INFINITY}.
   *
   * @return Minimum resulting value.
   */
  double getMin();

  /**
   * Get maximum resulting value. May be {@link Double#NaN} or
   * {@link Double#POSITIVE_INFINITY}.
   *
   * @return Maximum resulting value.
   */
  double getMax();
}
