NAME:
	diffmag_wfc
 PURPOSE:
       this program makes differential magnitude plots of objects from a 
	'wfc' database produced from an unmerged file for different 
	classifications, for each ccd. 
	It produces a ps file or a gif file or outputs to screen
 CALLING SEQUENCE:
	diffmag_wfc,wfcdb,wfc_image[,ps=ps,gif=gif,col=col]
 INPUTS:
	wfcdb:The wfc database to be searched. Must start with 'dbase/... '
 OPTIONAL OUTPUT KEYOWRDS:
	wfc_image: the image 
	ps: file name of the output ps file 
	gif:root file name of the 4 output gif files. Only active if ps is 
		not set. (will have gif_1.gif, gif_1.gif,...)
	If neither set the output is sent to an IDL graphics window
	field: STRING: name of field ie directory where the wfc/ dir is
	dbase: if set, a database containg the histogram values by class (diff
		and cum) is created)
	noplot: if set, the only thing the program does is create the database,
		no plots are produced.
 EXAMPLE:
	diffmag_wfc,'wfc','r219698'[,ps='diff_i_wfc']
 CALLED PROCEDURES:
	astrolib procedures,select_classes,wcs_zpn,mk_plot_diff,oplot_diff,
	ogif,cgif,ops,cps,select_ccd,write_diffmag_dbd
 MODIFICATION HISTORY:
	31-Oct-2000  Original by Suzanne Aigrain
	12-Dec_2000  S. Aigrain Added dbase bit

(See /home/xmmssc/soft/idl/pro/wfcqc/diffmag_wfc.pro)