Whenever you change the scale to look at a graph in greater detail or from
farther back, or you shift the range of the axes so that the graph you just
drew will be centered, the screen must be cleared so that a new coordinate
grid can be drawn. So you're left with the viewing angle you wanted for that
graph, but the screen is blank. You shouldn't have to solve this problem by
retyping the whole equation again...and you don't. You can redraw the equation
much more easily by selecting "Last graph" in the "Redraw" menu. But with
AutoRedraw ON, you don't even have to do that.
As its name suggests, AutoRedraw will redraw the last equation you typed
in automatically when you change the scale or range. If you don't want a graph
redrawn, you can abort it by pressing ESC twice and you will be returned to
the menu. If you want to turn off AutoRedraw completely (say you'd rather
redraw all of the equations in the redraw queue instead of just the last
one...with AutoRedraw on you'd have to wait for the last equation to be
graphed twice, once by each function), just select "AutoToggle" under the
"Redraw" menu and answer "n" when asked if you want AutoRedraw on.
AutoRedraw is ON by default. You can change the default to OFF by using
the "/A" command line option (see GRAPHIT.DOC, Appendix A for a full
explanation of the command line arguments).
Press PgDn for more help on the Redraw Queue.
THE REDRAW QUEUE
Every time you type in an equation, the character string you typed and the
program's internal representation of that equation get stored in the redraw
queue. From this queue, or list, you can call up any of the last 20 equations
you typed to graph again with fewer keystrokes than retyping it. Or you can
redraw all of them or the just the last one you typed with even fewer
keystrokes. The equations in the queue are stored in an order that puts the
most-recently-used at the beginning and the least-recently-used at the end.
Hopefully, when the queue fills up, the equations that are bumped off the
queue at the end will be the ones you won't miss very much.
As explained in the previous sub-section, the screen clears whenever you
execute Range or a successful Scale (if you abort Scale the screen remains as
it was). If you execute either of these functions or clear the screen
accidentally with the Clear menu option, you can redraw the last equation (if
AutoRedraw hasn't already) by selecting "Last graph" under "Redraw", or you
can redraw all of the equations in the queue using "Redraw All" under the
"Redraw" menu. Note that the redraw function does not keep track of which
graphs are on the screen at any point in time so "redrawing all" may put more
(if you plotted many equations on the screen before the last one) or fewer (if
you cleared the queue) equations on the screen than there were before the
screen was cleared. Press PgDn for more help.
USING "PICK GRAPH"
The "Pick graph" option in the Redraw menu allows you to graph any of the
equations currently in the redraw queue. Because of the enormity of the buffer
that would be required to "remember" what was on the screen "behind" a list of
all the equations in the queue so the images there could be preserved in EGA
and VGA modes, the equation-viewing is limited to one at a time in a pop-up
box. If you would like to redraw the one shown, press enter. Or, if you have a
mouse, click the left button on the equation itself. If you want to look at
more, press any other key except Escape (or click on any point on the screen
outside of the box with the equation in it). When you have looked at all of
the equations in the queue, it recycles to the first equation again. If the
equations start looking familiar, you've probably reached the beginning again.
If you decide you don't want to redraw any of the equations presented for your
perusal, press Escape (or click the right mouse button) and the command will
be ignored. When you pick a graph, it is reinserted at the top of the redraw
queue, as you'll likely be working with it again in the future. So if you
scale the grid again, that graph will be Auto-Redrawn, and if you redraw the
last graph, that graph will be shown.
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄEnd of Redraw help. Press ESC to return to menu.ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ