2.10 The Plotter

Much of the data for SEDPAK is defined by two dimensional curves. For example, eustatic sea level variation is defined as a set of time-depth pairs. SEDPAK provides a tablet, called the plotter, in which parameters such as eustasy, rates of clastic sedimentation, and carbonate accumulation are represented graphically. Some plotters, e.g., Subsidence and Sea Level, allow entry and modification of data via that plotter. Other plotters, e.g., Composite Sea Level, are for viewing purposes only. Data displayed in these "view only" plotters are derived from other data and therefore, cannot be edited. A sample plotter for Subsidence is shown in Figure 2.10.1.

Figure 2.10.1. Sample plotter.

Selection of Subsidence from the SEDPAK EDIT menu (Figure 2.5.2) invokes the Subsidence plotter, as shown in Figure 2.10.1 (for a more complete discussion of Subsidence see Section 3.06). Note that the title of the plotter corresponds to the selection. The principal display area of the plotter may have a single two-dimensional graph or, as in this case, can contain several two dimensional graphs superimposed on each other. The axes are labeled appropriately for the type of parameter being displayed. The OK button updates the data currently on the plotter, keeping that data in a temporary file until the EDIT files are saved and closes that plotter. If the Apply button is pressed, changes to the plotter are temporarily saved without closing the plotter. Pressing the Abandon button causes changes on the plotter to be discarded, and the plotter returns to its original form, provided the OK or Apply buttons have not been activated. The Cancel button causes the plotter to close without modifying the data (leaving it as it was when the plotter was selected). Changes can also be discarded by closing the database (.db) file without saving it from the EDIT menu.

Note that several subsidence curves can be displayed simultaneously. Curves are displayed by selecting them from the lower scroll area to the right of the graph, labeled Select the curves to display. For the example shown in Figure 2.10.1, subsidence curves exist at the locations 147.4, 147.6, 188.9, 189.1, 194.7, 194.7, 194.9, 208.6, 208.8, 225, 225.2, 245 and 250, and others which are not in view. Curves 147.4 and 250 have been selected in the lower right window and are displayed on the graph. If a curve is to be edited, it is selected from the upper scroll area to the right which is labeled Select curve by its location. The selected curve is then highlighted in blue. Individual points can be grabbed with the left hand button of the mouse and dragged to a new position. Points are outlined in red have been selected on the accompanying data sheet (see Section 2.11).

The menu bar at the top of the plotter has four menus (Curves, Points, Options, and Print) that can be pulled down and/or torn off (Figure 2.10.2). As with all active pull-down and tear-off menus in SEDPAK, they can be activated by selecting them with the mouse or by typing the single letter mnemonics indicated by an underlined character. Typing this letter while the mouse is on the plotter invokes a variety of actions. For example, under the Curve pull-down or tear-off menu, typing "n" brings up a New Curve data sheet (see Section 2.04 for more details on mnemonics).

Figure 2.10.2. Curves

The Curves pull-down or tear-off menu enables curves to be created and deleted for parameters which have more than one curve (e.g., Subsidence and Sea Level). There are five menu items (Figure 2.10.2; Curves): New Curve, Copy Current Curve, Delete Current Curve, Rename Current Curve, and Simplify Current Curve.

Figure 2.10.3 Dialog for giving tag for new curve.

Figure 2.10.4. Dialog box for Simplify current curve.

The Points pull-down or tear-off menu (Figure 2.10.5) has two commands: Add Point and Delete Point.

Figure 2.10.5. Points

The Options pull-down and/or tear-off menu has three menu items (Figure 2.10.6).

Figure 2.10.6. Options

The points can be shown with No Lines (Figure 2.10.8) with a Straight Line (Figure 2.10.1), a Least Square Fit (Figure 2.10.9) and a Cubic Spline (Figure 2.10.10). This Cubic Spline Fit to the data points on the plotter provides a template to which more data points can be added to the plotter so as to produce a curvilinear distribution of the data. N.B. This latter functionality can be really helpful for avoiding problems associated with aliasing and/or too abrupt changes in rates. For instance, should the data values have too great a separation in either distance and/or time, then the curvilinear Cubic Spline and the addition of superimposed data points can be used to modulate these previously abrupt changes in rate or location.

Figure 2.10.7 Line Fit

Figure 2.10.8 Plotter with data points but no connecting lines.

Figure 2.10.9 Plotter with data points displayed with least square fit.

Figure 2.10.10 Plotter with data points connected with a cubic spline. Further data points can be added to by superimposing these on this curve, so adding to the density of the data to reduce unrealistic abrupt changes in rates.

The Print pull-down or tear-off menu (Figure 2.10.11) enables printing of the graph either to a printer or to a file. Print to printer executes the print command located in the .sedpakrc file, which has been provided as part of the SEDPAK distribution. You or your system manager should modify this to conform to your environment. Print to Postscript file invokes a file selection dialog similar to the one in Figure 2.6.1. The directory may be selected and a name given for the file. Press OK to write the file.

Figure 2.10.11 Print

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2.11 The Data Sheet

Graphical data displayed in the plotter may also be viewed in a Data Sheet (Figure 2.11.1) which presents the data in a tabular format. Selection of Show Data Sheet from the Options pull-down menu causes the data sheet for Subsidence to be displayed, as shown in Figure 2.11.1. Note that the title of the data sheet indicates that it is associated with the Subsidence plotter and that this data sheet is for location 147.4. The curve can be renamed by selecting the name with the cursor and using the standard text editing features of the X window system. To move around within the data sheet use the four arrow keys on the keyboard or select a specific cell by clicking the mouse button when the mouse pointer is located in the proper cell. The data sheet has two columns of numbers because it is associated with a two dimensional graph in the plotter. The columns of the data sheet are labeled appropriately for the data (time and rate in the case of Subsidence). Tables (similar to data sheets) that have more than two columns and are used are available for summarizing data with several curves e.g., Depositional Distance (Section 3.08), but cannot be edited. In this case, there is no associated plotter.

Figure 2.11.1. Sample data sheet.

At the base of the data sheet are two rows of buttons (Figure 2.11.1).

Figure 2.11.2. Create Range dialog box.

In addition to the Create Range system of entry, data entry can also be accomplished by entering values into the various rows and columns of the data sheet. The fastest way to type entries to the data sheet is to type an entry and then move to the next entry by using the arrow keys. Pressing the Apply button sorts the rows, such that the left column (the x-coordinate of the graph) is in increasing numerical order. Note that the value in the cell that has been selected appears in the Cell Value field below the table.

Editing data points already in the data sheet can be accomplished in several ways. For instance after selecting the cell to be modified, use the mouse to locate the text cursor in the Cell Value field. The field can now be edited using the standard features of the X Window System. An alternate approach is to re-type the new value in the selected cell. Selecting a cell which already has a value and typing a new entry destroys the old value and replaces it with the newly entered one. The user can edit a new cell by using either the mouse or the arrows on the numeric keypad of the keyboard. After data entry the values of cells can be changed by selecting them and using the calculator (Section 2.12).

The data sheet is particularly important for editing surfaces from Surface Snapshot in the Basin Surface and Deposition from out of plane plotters (see Section 2.10). These imported surfaces can be defined by too many points to make their editing on a plotter easy. These extraneous points are removed by using the simplify current curve function attached to the plotter and by selecting large blocks of unwanted cells on the data sheet and deleting their contents.

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2.12 The Calculator

When the Calculator is selected from a data sheet, it is titled for the parameter being edited e.g. Subsidence Calculator, Sea Level Calculator, etc. This calculator, (Figure 2.12.1), allows generalized and cyclic numeric operations to be performed upon the data displayed in its companion data sheet and plotter. When the Constant Value button is activated, the value of the number which has been placed in the active window of the calculator is used as the operand for addition, subtraction, multiplication, or division operations on a cell or set of cells that have been selected within the data sheet with the mouse. An entire row of the data sheet can be selected for manipulation by the calculator by clicking on the row label to the left of the data sheet. For instance, an entire column can be selected by clicking on the column label at the top of the sheet; and several rows and/or columns, or portions of them can also be selected by clicking and dragging the mouse. Once a cell or a group of cells have been selected and a Constant Value entered, the appropriate operation is set on the calculator to multiply, divide, add or subtract. The Apply button should be pressed to update and view the effects of the operation on the data sheet. The calculator will remain active so that other operations can be applied, or if OK is pressed, the operation selected on the calculator is applied again to the data sheet and the calculator is dismissed. Cancel dismisses the calculator without changing the data sheet. N. B., once Apply is pressed, dismissing the calculator with OK will apply another calculation to the data sheet before the calculator closes.

Figure 2.12.1. Sample calculator.

For cyclic data calculations the Cycle Description button of the calculator is depressed and the Cyclic Data Entry dialog (Figure 2.12.2) is activated. This cyclic portion of the calculator can be used on selected groups of cells on the data sheet which exceed two in number. Its most effective use is on cells whose range is broken into equal "x" increments, preferably matching the time steps of the simulation. This range of values can be created on the data sheet (see Section 2.11) using the Create Range button. The Cyclic Data Entry dialog box (Figure 2.12.2) defines Sine or Sawtooth functions of unity which can be used to multiply, divide, or be added or subtracted from the selected range of "x" values on the data sheet. The Amplitude, Period, Phase, Positive and Negative Damping and Asymmetry can all be set. The dimensions of Positive and Negative Damping and Asymmetry are controlled by clicking the mouse to one side of the scroll bar, this bar will move towards the mouse arrow by a unit for each click.

Figure 2.12.2. Cyclic Data Entry Dialog.

Figure 2.12.3. Sinusoidal component of the cyclic curve defined by the Cycle Description of the calculator.

Figure 2.12.4. Sawtooth component of the cyclic curve defined by the Cycle Description of the calculator.

Figure 2.12.5. Sinusoidal curve with Positive and Negative Damping functions. The sawtooth damping functions are handled similarly.

Figure 2.12.6 shows a sinusoidal curve which is convex down and for which positive damping (Figure 2.12.5), but no negative damping, has been applied.

Figure 2.12.6. Sinusoidal curve with Positive Damping but no Negative Damping.

The Asymmetry of the sawtooth curve refers to the peak position, while the Asymmetry of the sine curve refers to the position of the intersection with the x-axis. Figure 2.12.7. illustrates the results of different Asymmetry values.

Figure 2.12.7. Asymmetry for sawtooth and sinusoidal curves.

Some plotters, such as that for sea level, allow the display of several cyclic curves whose character can vary as a function of time. Others, such as Lagoonal Damping, only allow one curve to be displayed. The sea level plotter allows the display of multiple curves together or individually. A separate "View Only" Composite Sea Level plotter enables the superposition and summation of these curves into one curve. For parameters other than sea level, such as rates of clastic accumulation, the calculator enables the superposition of several curves with different frequencies, periods, amplitudes, damping, or symmetries. When these curves are superimposed, the collective product is retained on the data sheet and its companion plotter, but the record of the creation of these different curves is not retrievable. If data on these changes and different curves are to be retained, the Comment dialog box (Section 3.01) should be used to record the qualities of these curves. N. B. that aliasing of the cyclic data will occur if the "x" values are less than the duration of the time steps (see Section 7.02).

An Undo button is provided so that the data sheet can be restored to its state prior to an erroneous calculator operation and prior to the pressing of Apply on the data sheet. The calculator retains information for all the previously performed operations and their sequence for the current data sheet until Apply is pressed, so operations can be undone in reverse order. To Undo operations remember Apply should not have been pressed on the data sheet.

Zero as an operand is considered to be a special case. Division by zero is not allowed and multiplication by zero cannot be undone.

Chapter 2, Section 13

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