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DIGIPLOT.TXT
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1990-08-31
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DIGIPLOT
Version 1.0
Alexander Walter
1. Introduction and Summary of Capabilities
DIGIPLOT is a tool to digitize curves using a Hewlett-Packard (or
compatible) plotter. You insert a plot into the plotter bed and calibrate the
corners as prompted by DIGIPLOT. Thereafter, when you move the plotter pen
around your graph using the arrow keys on the plotter itself (pen up, of
course!), DIGIPLOT continuously polls the plotter for its pen position.
DIGIPLOT interpolates, extrapolates, and scales the plotter pen coordinates to
your user coordinates. DIGIPLOT provides a continuous readout of the plotter
(x,y) coordinates and your user (x,y) coordinates.
DIGIPLOT can be used any time you have an (x,y) curve (such as
engineering data, or stock market prices over time) but not the tabular values.
DIGIPLOT will generate the tabular values at any points you like, and save them
to a file. DIGIPLOT will handle curves which are rotated; i.e., the X-axis and
Y-axis are not aligned with the physical edges of the page. Your plots can also
be portrait or landscape, backwards or forwards. DIGIPLOT can handle it!
If you find out later you made a mistake calibrating a curve (say you
missed the decimal point or swapped two digits) DIGIPLOT is smart enough to
allow you to go back and adjust your table of X,Y values without having to redo
the plot!
If you have a family of curves on the same page, DIGIPLOT can reuse the
same calibration data. Or if you have a series of similar plots on different
pages, where the position is slightly different on each page, DIGIPLOT can
position itself during calibration to the corners of the previous plot.
2. Digitizing a New Plot
This section describes the way to set up DIGIPLOT to digitize a new
curve.
2.1. Calibrating Your Plot
At any point while calibrating your plot, pressing ESC will return you
to the main menu.
You will first be asked to supply a file name. DIGIPLOT will store
calibration data and the X,Y user coordinates in this file.
You then tell DIGIPLOT the orientation of the plot in the plotter bed,
to the nearest 90 degrees, as viewed when facing the front of the plotter. The
valid choices are:
1. Portrait facing forward
2. Landscape facing left
3. Portrait facing backward
4. Landscape facing right
If you have a CGA or better display, the choices will be displayed
graphically. You will see a display similar to this:
2: Y
1: Y│ ┌─────────────
│ │
│ │
│ │
│ │
└──────────── X│
X
3: X 4:
────────────┐ │ X
│ │
│ │
│ │
│ │
│Y ──────────────┘
Y
This represents the four orientations in 90 degree increments. "X" and
"Y" in the graphic above represent the positive X-axis and positive Y-axis. The
numbering of the orientations corresponds to the listing given above.
You then need to go to the lower right-hand corner of your plot.
Depending on how your plot is oriented in the plotter bed, the lower right-hand
corner of the plot may not be in the physical lower-right hand corner as you
look at the plotter. For instance, in orientation 2 shown above, the lower
right corner of the plot is physically located in the lower left corner as it
is oriented in the plotter bed. Pressing ENTER tells DIGIPLOT you are at the
corner. You will then need to enter your user X,Y coordinates for the corner.
DIGIPLOT then prompts you to repeat the calibration process at the upper
left corner. If your user coordinate do not make sense with the orientation you
indicated (e.g., you indicated an orientation of "Portrait facing forward", but
the X-coordinate in the lower right corner is less than the X-coordinate in the
upper left corner) DIGIPLOT will not accept the erroneous calibration.
When calibration is completed, you can then move the plotter pen around
using the arrow keys on the plotter. Alternatively, you can move the plotter
pen around in fixed increments using the arrow keys on the PC keyboard. In
order to write a (X,Y) point to the data file, simply press ENTER. A running
count of how many points have been written is displayed. When you are done
digitizing, press ESC.
At any point while digitizing, you can temporarily escape to DOS by
pressing ALT-D.
2.2. Rotating the Plot
If your plot is rotated (i.e., the X-axis and Y-axis are not parallel to
the physical edges of the page) you can handle this in DIGIPLOT by pressing
ALT-R. Upon doing so, you are given two choices:
1. Over true Lower Left corner of the plot
2. Over projection of the true Upper Left corner of the plot onto the
rotated X-axis
The first option informs DIGIPLOT that you are about to calibrate the
exact position of the lower left corner of your plot. Calibration proceeds
similarly to the lower right corner and upper left corner. In general this will
require moving both the horizontal and vertical pen motion keys.
The second option requires you to calibrate the lower left corner by
indicating the projection of the upper left corner onto the X-axis. The
advantage of this method over the first method is that you only need to move
the plotter pen in one coordinate, either horizontally or vertically. DIGIPLOT
will take care of calculating the true lower left corner.
2.3. Changing the Plotter Increment
You can also move the plotter pen by pressing the arrow keys on the PC
keyboard. DIGIPLOT will command the plotter to move from the current position
so that it follows the orientation and any rotation of your plot. The default
plotter increment per keypress is one-tenth the difference between the
upper-left and lower-right user coordinates, in both the X-axis and Y-axis.
This plotter increment can be changed by pressing F1 or F2. Negative increments
will not be accepted.
2.4. Readying for Another Plot
When you are done digitizing a plot, DIGIPLOT will ask whether you have
more plots, giving you the following choices:
1. New graph & new calibration.
2. New graph & new calibration. Reposition to corners automatically.
Must have new graph inserted in plotter bed already.
3. New graph & use previous calibration.
4. No more graphs to digitize.
The first choice will result in having to recalibrate the lower right
and upper left corners just as was done for the first plot. Make this choice if
your next plot is dissimilar to the first.
The second choice will also result in recalibrating the corners, but the
plotter pen will be moved automatically to the corners of the previous plot.
From there, make any fine adjustments and press ENTER to mark the corner. The
new plot must already be in the plotter bed before making this choice. Make
this choice if your new curve is very similar to the previous (i.e., same X and
Y scales) but is on a different sheet of paper. You can also make this choice
if your new curve is on the same sheet of paper, but uses different scales.
The third choice will use the previous curve's calibration. Make this
choice if you are digitizing a family of curves printed on the same physical
piece of paper.
The fourth choice will return you to the main menu.
3. Correcting Coordinates on an Old Plot
This option will adjust the (X,Y) data points in the file you specify to
a new set of calibration points. Use this if you discover an error in
calibrating the corners after you have digitized a curve. Such an error could
arise from:
- Wrong user X or Y value inputted at a corner while calibrating
(transposed digits, wrong decimal place, etc.).
- Wrong tick mark on the X or Y axis used when positioning the plotter
pen.
DIGIPLOT will ask for the input filename. The data in it will be
interpolated, extrapolated, and scaled to fit the new calibration coordinates.
The new data will be written to a new file with the suffix ".NEW". It will
overwrite the file if it already exists. The original data file is kept without
changes.
DIGIPLOT must have the calibration header which it automatically inserts
into the data file. Not that this calibration header provides a convenient
check in case you suspect a corner was miscalibrated.
4. Change the COM Port
This choice allows the COM port to be changed. Invalid choices will be
automatically detected by DIGIPLOT and will not be accepted.
5. Quitting DIGIPLOT
This option will will exit DIGIPLOT and will display the following
message:
If you find this shareware product useful, please send
your $20 registration to:
Alexander Walter
182 ILER Dr.
Middletown, NJ. 07748
(908) 389-6755 9 AM - 5 PM EDT
(908) 671-5080 otherwise
Free upgrades to those who register.