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Routine Descriptions

CHIANTI_DEM

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 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 Name        : CHIANTI_DEM
     		          
 Purpose     : Calculates the Differential Emission Measure DEM(T) using 
		the CHIANTI database, from a given set of observed lines.
		Constant pressure or density can be used.

 Category    : diagnostic analysis
               
 Explanation : This routine has several options, all in the form of keywords.
 		First, the input file with the observed fluxes is read.
		THE FIRST TIME YOU USE THIS ROUTINE
		you'll have to do the calculation of the contribution
		functions G(T), so the routine GET_CONTRIBUTIONS will come 
		into play. You'll have to specify the value of the 
		pressure or density, and  you'll be asked to select an  
		ionization equilibrium file and an abundance file.
		GET_CONTRIBUTIONS searches the CHIANTI database (ion per ion) 
		for all the theoretical lines corresponding to the observed 
		lines, i.e. that lie in a OBS_WVL(i) +/- DELTA_LAMBDA_OBS(i) 
		interval centered on the observed wavelength OBS_WVL(i).
		The routine calculates the C(T) values (G(T)=Ab(element)*C(T))
		for the temperature interval log(T)= 4.0 - 8.0  
		with steps of log(T) = 0.1 .
		You can either select a constant pressure OR a constant 
		density for all the lines; if you select a constant pressure,
               for each ion the contribution function is calculated at an 
               electron density N_e equal to the ratio of the pressure 
               and the temperature of maximum ionization fraction:  
               C=C( T, N_e= P/T_ion )  
               The C(T) values are stored by GET_CONTRIBUTIONS in the output 
		file OUTPUT.CONTRIBUTIONS that can be used later to calculate
		the DEM, changing various parameters,
		without having to start again and read the CHIANTI database,
		which can take long time.

		In the case no theoretical lines corresponding to an observed
		line are found, the routine writes the wavelength of the line
		(to be excluded from the fit) in the array
		EXCLU_OBS_WVL_NO_TEO. The lines with no theoretical 
		counterparts are then automatically  excluded from the fit by 
	 	CHIANTI_DEM. You might consider the possibility to start again
		incrementing the DELTA_LAMBDA_OBS, to see if there are 
		theoretical lines in the vicinity.
		Note: if you want to exclude some of the observed lines from 
		the fit, you just have to use the keyword EXCLUDE_OBS_WVL, 
		BUT  GET_CONTRIBUTIONS will store anyway the results (if any)
		in the C(T) file.

		After having excluded the lines in EXCLUDE_OBS_WVL, 
		any *.abund file present in the CHIANTI database or in 
		the working directory can be selected, and eventually edited,
		if you like to change some abundances. 
		Then the $G(T)$ are calculated, multiplying each theoretical
		line by the abundance factor. Then the
		theoretical lines contributing to each blend are sorted by
		intensity and then their G(T) can be plotted if the keyword
		PLOT_GT is activated. It is recommended to do this the first 
		time, to check if there are some observed lines terribly 
		blended with lines of other elements, in which case it is
		better to exclude them with a second run (if you are not 
		sure about the abundances).
		Then the G(T) for each blend are summed and plotted.
		Then  the fit starts calling DEM_FIT. 
		A series of parameters can change the 
		result (DEM), especially the number and position of the mesh
		points of the spline that represents the DEM. The keyword
		MESH_POINTS serves for this purpose. 
		The other keywords that control the fit are N_ITER, DCHISQ_M.
   		At the end of the fit, the files OUTPUT.DEM and OUTPUT.GENERAL
		are created.



 Use         : IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
				pressure=3.e15


 Examples    : 
		Assume you have a file input 'serts89.obs' like this:
		
		243.031   491.    97.    0.1  He II
		256.323   1580.   186.   0.1  He II b
		315.024   253.    31.    0.1  Mg VIII
		335.401   10400.  1650.  0.1  Fe XVI
		319.839   113.    14.    0.1  Si VIII
		356.027   218.    25.    0.1  Si X 
		
		IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
		   pressure=3.e15,cut_gt=1e-30,/plot_gt

		After having selected the  ionization file,
		the C(T) (with MAX(C(T)) gt 1e-30)  are stored in the file
		'serts89.contributions'. Then select one of the abundance 
		files. 
		Have a look at the plots of the  G(T), and annotate
		if there is a line you want to exclude, let's say the second.
		Have a look at the DEM obtained ('serts89.dem') and at 
		the details contained in the file 'serts89.general'. 
		Maybe there is another line you want to exclude, let's say 
		the last one. Maybe you want to change the mesh points, too.
		So run
		IDL>chianti_dem,output='serts89_2',file_input='serts89.obs',$
		file_gt='serts89.contributions',$
		exclude_obs_wvl=[243.031,356.027 ],$
		mesh_points= [4.5,5.,5.5,6.2,7.5]
		
		The files 'serts89_2.dem' and 'serts89_2.general' will be
		created. They have the essential information about what you 
		did.

    
 Inputs      : various, all in form of keywords. The required ones are 
		OUTPUT and FILE_GT (or  PRESSURE/DENSITY)
               
               
 Opt. Inputs : various... see the software note.
               
 Outputs     : OUTPUT.CONTRIBUTIONS  
		Created only if the keyword FILE_GT is NOT set. 
		Is the file where all the contribution  functions G(T) are 
		stored. In the first two lines  the ionization equilibrium 
		file name, and the constant value of pressure or density 
		adopted are reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
		ionization stage, then the C(T) values. At the end the 
		specification for each transition.

		OUTPUT.DEM
		Is the file where the log T and log DEM values are 
		written, with a format suitable 
		as input for the DMM_SS procedure,that calculates the 
		synthetic spectrum. At the end some info on how it was 
		calculated are printed.

		OUTPUT.GENERAL
		Is the file where general information is stored.
		The abundance file, the ionization equilibrium file and the
		constant value of pressure or density  used are reported. 
		Then there is one line for each
		observed line, with the provisional identification, the 
		observed wavelength, the observed flux, the theoretical one
		(corresponding to the DEM), the error on the flux,
		the square of the difference between the theoretical and the 
		observed fluxes divided by the error (this number should be 
		close to zero if the line is well reproduced), and finally
		the ratio of the theoretical flux versus the observed one 
		(which should be close to 1).
		After this line, there is one line per each theoretical line
		contributing to the blend, with the identification, the 
		theoretical wavelength, the configuration and terms, and the
		contribution to the total theoretical flux (in percentage) 
		of each line in the blend.

		OUTPUT.OUT
		This file , toghether with OUTPUT.DEM , 
		can be used to reproduce the results  using 
		user-written software. See the software notes.
		The ouput has this format: 
		format='(a20,1x, 1f10.3,1x, 3e10.3, 1x,  f4.2,1x,f6.3)'	
	
 Opt. Outputs:
		An abundance file with the modifications inserted.
	
		Postscript files of the G(T).
	
		A postscript file with the DEM (OUTPUT.DEM.PS)
		
               A postscript file with other plots too (OUTPUT_4PLOTS.PS)

 Keywords    : 


	ARCSEC: 
		optional. If set, it means that the intensities in the input
		file are per arcsec-2 .
		These intensities are then  converted to 
		 sterad-1 .

	CUT_GT:	
		optional. If set, only the those theoretical lines that
		have a MAX(C(T))  greater than the value set, are kept; 
		it is useful to set this value in order to reduce the number 
		of lines in the file where the C(T) are stored.;  
		if not set, a default value of 1e-30 is adopted.

	DCHISQ_M:
		optional. If not set, a default value of DCHISQ_MIN=1.e-5 
		is assumed. For each iteration, the CHISQ and it's variation 
		are calculated. As long as the iteration achieves an
		improvement in CHISQ greater than  DCHISQ_MIN , another 
		iteration will be performed.

	DEM_FILE:
		optional.If set (,/DEM_FILE) you have to choose a DEM file to 
		be used as a start, instead of the default constant value of 
		10.^22.
		You can either choose one of the files in the CHIANTI database
		or any you have in the working directory. 
		The values in the file are marked as crosses, the mesh points
		are marked with triangles.

	DENSITY : 
		the value of the density (Ne). Required if you do NOT have
		already the contribution  functions G(T). 

	EXCLUDE_OBS_WVL:
		optional.
		If set, you can  exclude some of the observed lines from 
               the fit. Note that even if you set this keyword and run 
		GET_CONTRIBUTIONS all the theoretical lines found corresponding
		to all the lines in the input file are written in the C(T) 
		file. It is only in the fit that the lines are excluded.

	FILE_GT:
		optional.
		If NOT set, the routine GET_CONTRIBUTIONS is called.
               If set, it has to specify the name of the file created by 
		GET_CONTRIBUTIONS, where all the contribution  functions G(T) 
               are stored. In the first two lines the ionization equilibrium 
		file name, and the value of the pressure or density 
               adopted is reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
               ionization stage, then the C(T) values. At the end the 
               specification for each transition.

	FILE_INPUT:
		optional.
 		if set, you are not requested to select the observation file
		using a widget-type search.
		The input file  must contain 5 columns, unformatted:
		1)the observed wavelength (A)
		2)the observed flux in erg cm-2 s-1 st-1
		3)the corresponding error on the flux in erg cm-2 s-1 st-1
		4)half the width (A) of the range (centered on the observed 
		  wavelength) where you want to look for the corresponding 
		  theoretical lines. A value of HWHM or more would do.
		5)The identification, written as string (max 20 characters)

	MESH_POINTS:    	
		optional. It is a vector that specifies the mesh points for the
		spline that represent the fitted DEM, in log(T).
		If not set, the default values 
		[4.,4.5,5.,5.5,6.,6.5,7.,7.5,8.0] are assumed.

	N_ITER:
		optional.It is the number of iterations of the fitting routine.
		If not set, a default value of 20 is assumed. 
		Changing this value alone might not affect the fit, since 
		also the value of DCHISQ_MIN is checked during the fit.

	N_MATCHES:   
		optional.          
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

	OUTPUT  :
		required.
	  	It is the output name. Suffixes will be added when creating 
		the various outputs.

	PHOT:
		optional.
		If set, it means that in the input file the intensities
		are in photons instead of ergs. 

	PLOT_GT:
		optional.
		If set (,/PLOT_GT),  plots of the  G(T) for each 
		observed line not excluded are created.

	PRESSURE:     		
		the value of the pressure (Ne T). Required if you do NOT have
		already the contribution  functions G(T).

	QUIET:
		optional. Set to avoid various messages and the details of the 
		result.

 Calls       : GET_CONTRIBUTIONS
		DEM_FIT
		ZION2SPECTROSCOPIC
		print2d_plot
		
 Common      : obs, 	obs_int,obs_sig,n_obs
		obs_o,	obs_wvl,obs_id,obs_delta_lambda
 		dem, 	d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh
		contr,	ch_tot_contr
		ab,	abund_name,abund_info,xuvtop,ioneq_name

		these are the commons with GET_CONTRIBUTIONS.PRO:

		various,	exclu_obs_wvl_no_teo,const_net,$
		 dem_temp_min,dem_temp_max,n_dem_temp,$
		 ch_wvl,ch_l1,ch_l2,ch_id,ch_z,ch_ion,ch_contr_wa,$
		 ch_pop,ch_contr_list,	 ch_term,ch_n_contr

 Restrictions: 
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

		Also, if the starting DEM values are not proper, or you 
		don't have enough constraints at lower and higher temperatures,
		you might get "strange" results, and should consider using 
		different starting values.

		Of course you need to have the enviroment variable CDS_SS_DERE
		pointing to the CHIANTI database top directory.

               
 Side effects: None known yet.
               
 Category    : spectrum
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  

 Written     : 
       V. 1.0  5 November  1997 Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK)


 Modified    : Removed the print2d_plot subroutine. Increased the default value
               of N_MATCHES from 20 to 50.  Changed way to deal with xuvtop.
               GDZ, 31-Oct-2000

 Version     : 2.0 GDZ, DAMTP,  31-Oct-2000

              V.3, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :  3, 21-May-2002, GDZ 

(See dem/chianti_dem.pro)


DEM_FIT

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 Project     : SOHO - CDS     
                   
 Name        : DEM_FIT
               
 Purpose     : Calculates the Differential Emission Measure DEM(T) using
		a set of values in common with other routines.
               
 Category    : diagnostic analysis

 Explanation : This routine (called by CHIANTI_DEM.PRO)   performs
		 a series of iterations in order to
		find the DEM that minimize the chi^2. The values in common 
		with CHIANTI_DEM.PRO are used.
		As a least squares fit to a non-linear
       	function, see pages 237-239, Bevington, Data Reduction and Error
       	Analysis for the Physical Sciences.
               
 Use         : IDL> dem_fit,y,chisqr 
		It has to be noted that a general use of this routine 
		is limited.
    
 Inputs      : the values stored in common. 
                              
 Opt. Inputs : None
               
 Outputs     : log_dem_mesh,y ,chisqr
		i.e. the DEM mesh values, the intensity values as resulted
		from this model DEM, and the chi^2.
 
               
 Opt. Outputs: None
               
 Keywords    : 
		FLAMBDA: the initial value of the parameter flambda.

		SCALE:   the initial value of the parameter scale, that 
			controls the steps of the iteration.

		N_ITER:
		optional.It is the number of iterations of the fitting routine.
		If not set, a default value of 20 is assumed. 
		Changing this value alone might not affect the fit, since 
		also the value of DCHISQ_MIN is checked during the fit.

		DCHISQ_M:
		optional. If not set, a default value of DCHISQ_MIN=1.e-5 
		is assumed. For each iteration, the CHISQ and it's variation 
		are calculated. As long as the iteration achieves an
		improvement in CHISQ greater than  DCHISQ_MIN , another 
		iteration will be performed.

		FAILED: If the fit fails,the routine returns and flags FAILED=1

		QUIET:
		optional. Set to avoid various messages

 Calls       : DEM_DERIV, DEM_FUNCTN, DEM_CHISQR

 Common      : 
               obs,  obs_int,obs_sig,n_obs
               dem,  d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh 
		contr,ch_tot_contr
               
 Restrictions: Not always the fit is successful.
               
 Side effects: None known.
               
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  

 Written     : 
       Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK)  5 November 1997

 HISTORY:

       Ver 1, GDZ  5-Nov-97

       Ver 2,  EL 6-Apr-05
               Renamed the variable "deriv" to "deriv1" to avoid conflicts
               with an IDL routine with the same name.
       
 Version     : 2.0  6 April 2005

(See dem/dem_fit.pro)


GET_CONTRIBUTIONS

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 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

     		          
 Purpose     : calculates the contribution functions G(T) at constant 
		pressure or density  of the lines present in the CHIANTI
		database, corresponding to  a given set of observed lines.

 Category    :
               
 Explanation : This routine is called by CHIANTI_DEM. It cannot be used as
		a stand-alone routine.
		The observation file is read by CHIANTI_DEM.
		GET_CONTRIBUTIONS starts reading 
		the ionization equilibrium file and the masterlist of the
		ions present in the CHIANTI database.
		GET_CONTRIBUTIONS  then searches the 
		CHIANTI database (ion per ion) for all the 
		theoretical lines corresponding to the observed	lines, i.e. 
		that lie in a OBS_WVL(i) +/- DELTA_LAMBDA_OBS(i) interval
		centered on the observed wavelength OBS_WVL(i).
		Then calculates the G(T) values for the temperature interval
		log(T)= 4.0 - 8.0  with steps of log(T) = 0.1
		A constant pressure OR a constant density for all the lines
 		is used. If you select a constant pressure,
               for each ion the contribution function is calculated at an 
               electron density N_e equal to the ratio of the pressure 
               and the temperature of maximum ionization fraction:  
               C=C( T, N_e = P/T_ion)
               The C(T) values are stored by GET_CONTRIBUTIONS in the output 
		file OUTPUT.CONTRIBUTIONS.

		In the case no theoretical lines corresponding to an observed
		line are found, the routine writes the wavelength of the line
		to be excluded from the fit in the array EXCLU_OBS_WVL_NO_TEO;
		these lines are then excluded from the fitting  by 
	 	CHIANTI_DEM. You might consider the possibility to start again
		incrementing the DELTA_LAMBDA_OBS, to see if there are 
		theoretical lines in the vicinity.


 Use         : called by CHIANTI_DEM to calculate the contribution functions

 Examples    : 

    
 Inputs      :	Various, in form of keywords.
               
               
 Opt. Inputs : none
               
 Outputs     : OUTPUT.CONTRIBUTIONS  
		Is the file where all the contribution  functions G(T) are 
		stored. In the first two lines  the ionization equilibrium 
		file name, and the constant value of pressure or density 
		adopted are reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
		ionization stage, then the C(T) values. At the end the 
		specification for each transition.


 Opt. Outputs: None
               
 Keywords    : (all passed by CHIANTI_DEM)


	CUT_GT:			if set, only those
				theoretical lines that have a MAX(G(T)) greater
      			        than the value set, are kept; it is useful to 
				set this value in order to reduce the number 
				of lines in the file where the G(T) are stored.

	DENSITY : 		the value of the density (Ne).

	FILE_INPUT:		if set, you are not 
				requested to select the observation file.

  
	N_MATCHES:              
		In the unlikely event that more than 20 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

	PRESSURE:     		the value of the pressure (Ne T)

	OUTPUT  :  	-the core name for the output


 Calls       : 
		READ_IONEQ 
               read_masterlist
		CONVERTNAME
               ion2spectroscopic
		ZION2FILENAME
		READ_WGFA2
		READ_SPLUPS
		POP_SOLVER
		READ_ELVLC
		READ_IONREC
		CONVERT_TERMS

 Common      : elvlc                          - energy levels
               wgfa                           - radiative data
               upsilon                        - upsilon data
		      
		obs, 	obs_int,obs_sig,n_obs
		obs_o,	obs_wvl,obs_id,obs_delta_lambda
 		dem, 	d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh
		contr,	ch_tot_contr
		ab,	abund_name,abund_info,xuvtop,ioneq_name

		these are the commons with GET_CONTRIBUTIONS.PRO:

		various,	exclu_obs_wvl_no_teo,const_net,$
		 dem_temp_min,dem_temp_max,n_dem_temp,$
		 ch_wvl,ch_l1,ch_l2,ch_id,ch_z,ch_ion,ch_contr_wa,$
		 ch_pop,ch_contr_list, ch_term,ch_n_contr


 Restrictions: ;
		THIS IS NOT A STAND-ALONE PROCEDURE. 
		It is called by CHIANTI_DEM,
		and has a lot of common blocks with other procedures.

		In the unlikely event that more than 20 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

		Of course you need to have the enviroment variable CDS_SS_DERE
		pointing to the CHIANTI database top directory.

               
 Side effects: None known.
               
 Category    : spectrum
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  
 Written     : 
       Version 1, Giulio Del Zanna (GDZ)  5 November  1997 
	UCLAN (University of Central Lancashire, UK) 

 Modified    :  
       Version 2, 31-Oct-2000, GDZ, DAMTP.  Rewritten completely the routine,
       to make it compatible with CHIANTI v.3. Based the core calculations on
       new implementations due to Peter Young, CfA. 

       Version 3, 5-Dec-2000, GDZ, DAMTP. Fixed a bug when checking the 
       values in the .splups files.


       Ver. 4,  25-Apr-02, GDZ  
              Revised to account for v.4 variations. By default the proton
              rates are included in the calculation of the level population.

       V.5, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V. 6,  10-July-2002  GDZ
                  Corrected a bug. It now properly includes by default the
                  proton rates in the population solver. 

       V. 7,  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure. 

       V. 8, 3-Nov-03  GDZ
                  Modified format e8.2 to e9.2 for Windows compatibility.

       V. 9, 4-May-05 Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER

       V.10, 12-Jun-2009, Enrico Landi
                  Changed the definition of the temperature array for ion fractions
                  in the IONREC variable, now taken directly from the output of
                  READ_IONEQ.PRO

 VERSION     :    10, 12-Jun-2009


(See dem/get_contributions.pro)


PLOT_DEM

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 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	PLOT_DEM

 PURPOSE:

	To plot differential emission measure (DEM) values

 CATEGORY:

	Widgets.

 CALLING SEQUENCE:

       PLOT_DEM,filename


 INPUTS:

	filename:  the name of the DEM file to be plotted.  The file must b
                  in the standard CHIANTI format for DEM files.  If filename 
                  is a blank string ('') then an interactive window will come 
                  up to allow the user to select a DEM file from the CHIANTI 
                  DEM directory or some other directory.	

	
 KEYWORD PARAMETERS:

	PSFILE:	If set, the a postscript plot will be place in the 
               file 'psfile' specified by the user


 OUTPUTS:

       None, other than a plot




 EXAMPLE:

             > plot_dem,'ademfile.dem'
         or
             > plot_dem,''

 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	June 1998:     Version 1.0
	Version 2, 21-Dec-2000, William Thompson, GSFC
		Modified for better cross-platform graphics capability

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 


(See dem/plot_dem.pro)