% @(#)overplhist.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:43:47
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      overplhist.hlq
%.AUTHOR     Rein H.Warmels, IPG/ESO
%.KEYWORDS   MIDAS, help files, OVERPLOT/HISTOGRAM
%.PURPOSE    On-line help file for the command: OVERPLOT/HISTOGRAM
%.VERSION    870609 RHW Creation
%----------------------------------------------------------------
\se
SECTION./HIST
\es\co
OVERPLOT/HISTOGRAM                                             10-JUN-1987  RHW
\oc\su
OVERPLOT/HISTOGRAM tab col [offset] [bin[,min[,max]]] [exc] [log] [opt]
	overplot histogram of a column in the table
OVERPLOT/HISTOGRAM frame [offset] [log] [opt]
	overplot the histogram of an image
\us\pu
Purpose:    
            Overplot a histogram of a column in a table or
            Overplot the histogram of given image
\up\sy
Syntax:     
            OVERPLOT/HISTOGRAM tab col [offset]  [log] [opt] [bin[,min[,max]]] 
                               [exc] [log] [opt]
            or
            OVERPLOT/HISTOGRAM frame [offset] [log] [opt]
\ys\pa
            tab =    name of table file
\ap\pa 
            col =    column reference
\ap\pa
            offset = offset in the ordinate direction (default 0.0)
\ap\pa
            bin,min,max = bin size, minimum, and maximum values to be included
                     in the histogram. Default bin size depends on the actual 
                     dynamic range of the data values; default minimum is the 
                     minimum of the column values; similar for maximum.
\ap\pa
            exc =    plot low and high excess; default YY
\ap\pa
            log =    flag for logarithmic scale; can be LIN (default) LOG 
                     or LN. 
\ap\pa      
            opt =    histogram type, hashing spacing and hashing angle; 
                     default: standard staircase plot, no hashing done.\\
                     The histogram type is determined by an integer number:
                       0:  simple staircase;\\
                       1: staircase steps joining the x axis;\\
                    => 2: data points will joint the x axis with boxes 
                          which are determined by the number (2 = zero width)\\
\\
                     In case the hashing spacing is given a small number 
                     (e.g. 0.01) the histogram will be filled completely. A 
                     reasonable number is 1.
\ap\pa
            frame  = name of image frame
\ap\no
Note:    
            In case the second parameter is defaulted, the command assumes a
            frame as input.
\\
	    In case the input  is a frame the command will first check if the 
            descriptor HISTOGRAM exits. If so, these data will be plotted. If 
            the descriptor is absent the command  STAT/IMAGE  will be executed
            first.
\\
            The histogram determination of a table column makes use of the 
            command READ/HISTOGRAM. The histogram data for tables is stored 
            in two descriptors of the table: TCLAS001 and TFREQ001.
\\
            After the overplot the last (over)plotted data set is the active
            one and subsequent commands will work on these data.
\on\see
See also:
            PLOT/HISTOGRAM, PRINT/HISTOGRAM, COMPUTE/HISTOGRAM, READ/HISTOGRAM,
            STAT/IMAGE
\ees\exs
Examples:
\ex
            OVERPLOT/HISTOGRAM myimage ? LOG
            This will overplot the descriptor HISTOGRAM of the image
            myimage.bdf with a logarithmic scale in y.
\xe\ex
            OVERPLOT/HISTOGRAM mytable :VELOCITY .5 1,8 NN ? 1,.5,90
            This will plot the column labelled :VELOCITY from table
            mytable.tbl with a y offset of .5 units; the bin size will be 1 
            and the minimum value will be 8. Excess bin are not plotted and
            the histogram is of the bar type and filled with vertical lines.
\xe \sxe