	      This is the help for Hgraph (2-d histogram)


INTRODUCTION
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The hgraph is a 2-d histogram, which is incremented via (x,y) points.
When (x,y) points are passed in, the corresponding box is incremented.
Frequencies of the histogram are represented by colors.  If a box is at
a high color on the color scale, this means this box has a high
frequency.  If the box is of a color at the lower end of the color
scale, this box has a lower frequency.

Color table         High Color         Low Color
------------        -----------        -------------
Blue-Yellow         Yellow             Blue
Blue-Red            Red                Blue
Yellow-Brown        Brown              Yellow

In the histogram, boxes will range in color.  However, when the
frequencies become further and further apart, a rescaling must be done
to keep the range of the colors in tact.  For example, if the color
range is blue-yellow and a box starts to turn extremely yellow.  This
means that this box is at the top of the color scale.  Once this box
goes over, a rescaling will be done and the box will now become a more
middle color (probably greyish).


FEATURES
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(1) One-Dimesional histogram

	The user may open a 1-d dimensional histogram as well.  Either
the x axis or the y axis may be projected on to this 1-d histogram by
use of the "project x axis" or "project y axis" button of the Options
menu.   The boxes of the 1-d histogram will grow as the frequency
increases.   The frequency of the box can be found by looking at the
y-axis of the 1-d histogram.  All 1-d histograms are closed when the
"close histogram" button is chosen in the File menu.

(2) Grid

	The 2-d histogram has a grid to make it easier to distinguish
the boxes.  However, the user may turn this grid off and on through a
button in the edit menu.

(3) Current Point

	The dot the user will see swimming around through the histogram
represents the current point entered into the histogram.  Again, the
user may turn this feature on or off by use of a button in the edit
menu.

(4) Write to File

	The user may write all of the points to a file by use of the
"write to file" button in the File menu.  The (x,y) point of the corner
of each box along with the frequency will be written to a file.

(5) Load from File

	The user may load data in from a file as well by use of the
"load from file" button in the File menu.  The format of the file must
be: 

	<x value> <y value> <frequency>

	A sample file may look like:

	0.4345  6.34424 45
	0.23 2.1144 32

(6) Close Histogram

	The user may close the histogram by use of the "close histogram"
button in the File menu.  This feature closes both the 2-d histograms
and other 1-d histograms that may have been opened.

(7) Change Colormap

	The user may change the colormap by user of the "change
colormap" button of the Edit menu.  The possible colormaps are:
blue-yellow, blue-red, and yellow-brown.  The choice of the colormap
determines what color the boxes of the histograms will be.

(8) Shift Axis

	The user may shift the histogram either up, down, right, or left
by use of the "shift axis" button of the Edit menu.  When this button is
clicked, an directional arrow box will be activated.  Just click on the
up arrow to move the histogram up, etc.  If the current point starts to
move off of the histogram, the user may want to use this to sort of
"follow" the point.

(9) Change histogram spacing

	The user may change the number of boxes by use of the "change
histogram spacing" button of the Edit menu.  When this button is
activated scales for both the x and the y axis will appear.  If the user
wants to decrease the number of regions along the x axis, move the scale
left.  To increase the number of regions, move the scale right.  The
number of regions for the y axis may be changed in the same manner.  The
increase of the regions will increase precision of the histogram.  For
example, if there was 3 regions on the x axis and 5 on the y axis, this
means there is a total of 15 boxes (3 x 5).  If increased to 5 on the x
axis and 8 on the y, the total boxes will be increase to 40 (5 x 8),
thus increasing precision of the histogram.

(10) Change data/display intervals

	The user may change the rate at which the data is entered into
the histogram and the rate at which the data is displayed by use of the
"change data/display intervals" button in the Edit menu.  When this
button is activated, two scales will appear, one for changing the
display rate and one for changing the data entry rate.  The current
setting for both will be at 1, which means every point will be entered
and displayed.  To increase, move the scale right.  To decrease, move
the scale left.  If the display interval is changed to 3, for example,
this means that the histogram will be updated every third point.  If the
data interval is changed to 4, this means that only every fourth point
will be entered into the histogram.

(11) Clear the histogram

	The histogram may be cleared by use of the "clear histogram"
button of the Edit menu.  This means all frequencies will be set to zero
and the 2-d histogram and any 1-d histograms will be erased (all boxes
will be white).

