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: Y³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄ X³ X 3: X 4: ÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ X ³ ³ ³ ³ ³ ³ ³ ³ ³Y ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ 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.