C @(#)logistic.for	17.1.1.1 (ES0-DMD) 01/25/02 17:10:49
C===========================================================================
C Copyright (C) 1995 European Southern Observatory (ESO)
C
C This program is free software; you can redistribute it and/or 
C modify it under the terms of the GNU General Public License as 
C published by the Free Software Foundation; either version 2 of 
C the License, or (at your option) any later version.
C
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
C GNU General Public License for more details.
C
C You should have received a copy of the GNU General Public 
C License along with this program; if not, write to the Free 
C Software Foundation, Inc., 675 Massachusetss Ave, Cambridge, 
C MA 02139, USA.
C
C Corresponding concerning ESO-MIDAS should be addressed as follows:
C	Internet e-mail: midas@eso.org
C	Postal address: European Southern Observatory
C			Data Management Division 
C			Karl-Schwarzschild-Strasse 2
C			D 85748 Garching bei Muenchen 
C			GERMANY
C===========================================================================
C
      SUBROUTINE LOGIST(IND,X,NP,P,Y1,D)                                      
C+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                  
C.COPYRIGHT: Copyright (c) 1987 European Southern Observatory,                  
C                                         all rights reserved                   
C                                                                               
C.VERSION: 1.0  ESO-FORTRAN Conversion, AA  18:01 - 21 DEC 1987                 
C                                                                               
C.LANGUAGE: F77+ESOext                                                          
C                                                                               
C.AUTHOR: J.D.PONZ                                                              
C                                                                               
C--------------------------------------------------------------                 
C                                                                               
C LOGISTIC DISTRIBUTION                                                         
C      IMPLICIT NONE                                                            
C                                                                               
C Y1 = 4.*P(1)*EXP(-ABS(X-P(2))/P(3))/(1.+EXP(-ABS(X-P(2))/P(3)))**2            
C                                                                               
      INTEGER NP,IND
      DOUBLE PRECISION Y1,P(NP),D(NP),A,B,C,E,F,G                               
      REAL X(1)                                                                 
C                                                                               
      A      = X(1) - P(2)                                                      
      B      = 1.76274716/P(3)                                                  
      C      = B*DABS(A)                                                        
      E      = DEXP(-C)                                                         
      F      = 1. + E                                                           
      D(1)   = 4.*E/ (F*F)                                                      
      Y1     = D(1)*P(1)                                                        
      G      = (1.0-E)*Y1/F                                                     
      D(2)   = DSIGN(G*B,A)                                                     
      D(3)   = G*C/P(3)                                                         
      RETURN                                                                    
                                                                                
      END