NAME:
       EFAREA
 PURPOSE:
	Calculate the FCS effective area
 CATEGORY:
       Calibration
 CALLING SEQUENCE:
       area=efarea(wavlen,ichan,xtemp)
 INPUTS:
       wavlen= wavelength scalar (A)
       ichan = FCS detector (1-7)
       xtemp = XTAL bank temperature 
 OPTIONAL INPUT PARAMETERS:
       none
 OUTPUTS:
       FCS effective area (cm^2)
 OPTIONAL OUTPUT PARAMETERS:
       none
 CALLS: ***
	FCS_WINDOW, TWOD
 CALLED BY:
	fcs_par, fluxcon
 SIDE EFFECTS:
       none
 RESTRICTIONS:
       none
 PROCEDURE:
	EFAREA now calls the function FCS_WINDOW to compute
	the window transmission.  
 MODIFICATION HISTORY:
	9  Jun 1982,	Fortran Program: Written, J.W. Leibacher, LPARL
	20 Jun 1985,	Written, R.A. Stern, LPARL
	25 Feb 1988, 	J.R. Lemen, LPARL

 NAME:
	ERR_PLOT

 PURPOSE:
	Plot error bars over a previously drawn plot.

 CATEGORY:
	GRAPHICS

 CALLING SEQUENCE:
	ERR_PLOT, Low, High	;X axis = point number.

	ERR_PLOT, X, Low, High	;To explicitly specify abscissae.

 INPUTS:
	Low:	A vector of lower estimates, equal to data - error.
	High:	A vector of upper estimates, equal to data + error.

 OPTIONAL INPUT PARAMETERS:
	X:	A vector containing the abscissae.

 KEYWORD Parameters:
	WIDTH:	The width of the error bars.  The default is 1% of plot width.

 CALLED BY:
	Data Display, HXRBS
 SIDE EFFECTS:
	An overplot is produced.

 RESTRICTIONS:
	Logarithmic restriction removed.

 PROCEDURE:
	Error bars are drawn for each element.

 	Examples:
	To plot symmetrical error bars where Y = data values and 
	ERR = symmetrical error estimates, enter:

		PLOT, Y			;Plot data
		ERR_PLOT, Y-ERR, Y+ERR	;Overplot error bars.

	If error estimates are non-symetrical, enter:

		PLOT,Y
		ERR_PLOT, Upper, Lower	;Where Upper & Lower are bounds.

	To plot versus a vector of abscissae:

		PLOT, X, Y		  ;Plot data (X versus Y).
		ERR_PLOT, X, Y-ERR, Y+ERR  ;Overplot error estimates.

 MODIFICATION HISTORY:
       Based on errplot.pro from the IDL library
       Mod. 03/96 by RCJ.  Added _extra keyword.
	Mod. 05/15/96 by RCJ. Added documentation.