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/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see .
 */

package weka.classifiers.neural.common.transfer;

import weka.core.Tag;

/**
 * Title: Weka Neural Implementation
 * Description: ...
 * Copyright: Copyright (c) 2003
 * Company: N/A
 *
 * @author Jason Brownlee
 * @version 1.0
 */

public class TransferFunctionFactory {

  public static final int TRANSFER_SIGMOID = +1;

  public static final int TRANSFER_TANH = +2;

  public static final int TRANSFER_SIGN = +3;

  public static final int TRANSFER_STEP = +4;

  public static final int TRANSFER_GAUSSIAN = +5;

  public final static String[] TRANSFER_FUNCTION_FULL_DESC =
    {
      "Sigmoid (Logistic), S-shape function between +1 and 0",
      "Tanh (Hyperbolic Tangent), S-shape function between +1 and -1",
      "Sign Function (Bi-poler Step) (<= 0) == -1, (> 0) == +1",
      "Step Function (<= 0) == 0, (> 0) == +1",
      "Gaussian Function, Hump shape function between +1 and 0"
    };

  public static String getDescriptionForFunction(int function) {
    return TRANSFER_FUNCTION_FULL_DESC[function - 1];
  }


  // tags for transfer function
  public final static Tag[] TAGS_TRANSFER_FUNCTION =
    {
      new Tag(TRANSFER_SIGMOID, "Sigmoid (Logistic)"),
      new Tag(TRANSFER_TANH, "Tanh (Hyperbolic Tangent)"),
      new Tag(TRANSFER_SIGN, "Sign Function (Bi-poler Step)"),
      new Tag(TRANSFER_STEP, "Step Function"),
      new Tag(TRANSFER_GAUSSIAN, "Gaussian Function")
    };


  public final static String DESCRIPTION;

  static {
    StringBuilder buffer = new StringBuilder();
    buffer.append("(");

    for (int i = 0; i < TAGS_TRANSFER_FUNCTION.length; i++) {
      buffer.append(TAGS_TRANSFER_FUNCTION[i].getID());
      buffer.append("==");
      buffer.append(TAGS_TRANSFER_FUNCTION[i].getReadable());

      if (i != TAGS_TRANSFER_FUNCTION.length - 1) {
	buffer.append(", ");
      }
    }
    buffer.append(")");

    DESCRIPTION = buffer.toString();
  }


  public static TransferFunction factory(int selection) {
    TransferFunction transfer = null;

    switch (selection) {
      case TRANSFER_SIGMOID: {
	transfer = new SigmoidTransferFunction();
	break;
      }
      case TRANSFER_TANH: {
	transfer = new HyperbolicTangentTransferFunction();
	break;
      }
      case TRANSFER_SIGN: {
	transfer = new SignTransferFunction();
	break;
      }
      case TRANSFER_STEP: {
	transfer = new StepTransferFunction();
	break;
      }
      case TRANSFER_GAUSSIAN: {
	transfer = new GaussianTransferFunction();
	break;
      }
      default: {
	throw new RuntimeException("Unknown transfer function: " + selection);
      }
    }

    return transfer;
  }
}