Graphing

CurveExpert has extensive graphing capability. This capability gives you immediate feedback on the performance of a particular data model.

Graphing Window Overview

CurveExpert allows you to open many graphing windows at one time so that you may compare different curve fits. Note that changes that you might make to a particular graphing window will affect only that window. See the Graph Properties dialog to see how to apply your changes to all plots, as well as saving your customizations for future use.

Each graph has a consistent user interface. Press the right mouse button to obtain the graphing menu, which gives you access to all of the functions available for plots, such as customizing the plot, obtaining model information, analyzing the model, or printing the plot. Zooming and panning are controlled by dragging a rectangle across the graph pane and/or pressing the arrow keys. Any plot can be autoscaled by pressing Shift+A .

The most vital piece of information that you might want to access are the values of the model parameters. Press the Info button, select Information from the graphing menu (by clicking the right mouse button), or press Ctrl-I to access this (as well as other) information. Note that if the graph title is displayed, the Info button is not available; choose Information from the graphing menu or press Ctrl-I to access the curve fit information.

Graphs can be customized by selecting Graph Properties from the graphing menu.

It is possible that CurveExpert will not be able to properly draw your graph. For example, the y-extents might be negative on a graph that is being drawn with log axes. Or, the extents might be set such that a singularity in the model exists somewhere in the domain. CurveExpert will notify you of these occurrences with a error message printed on the graphing surface. In these cases, reset the graphing extents using the XY Axis Properties section of the Graph Properties dialog (accessed via the popup menu described below).

Graphing Controls

• Zoom: You may zoom in on a region on the graph by holding down the left mouse button, dragging over the area of interest from top left to bottom right, and then releasing the button. Likewise, zoom out by holding down the left mouse button, dragging from bottom right to top left, and then releasing the button. Zooming out will cause the entire graphing area to be enclosed in the rectangle that was made by dragging “backwards.” Note: Zooming is not available on log or semilog plots. Also note that any zoom that starts or ends outside of the graphing pane will be ignored.
• Pan: To pan the graph in any direction, press the arrow keys. This will pan the graph in the direction that you choose by a magnitude of the major tick length. Holding SHIFT while pressing the arrow keys gives you finer control by only panning one minor tick length. Note: panning in the direction of a log scaled axis is not supported.
• AutoScale: Press SHIFT-A to autoscale the graph. Autoscaling guarantees that every data point on the plot will be shown, which is the default for a newly opened graphing window.

Graphing Menu and Shortcuts

By pressing the right mouse button or by pressing Ctrl-M in any graphing window, you can pick from the graphing menu (keyboard equivalents are listed also):

• [Ctrl-W] Find Main Window
• [Ctrl-G] Graph Properties
• [Ctrl-I] Information
• [Ctrl-T] Generate Table
• [Ctrl-L] Analyze
• [Ctrl-C] Copy
• [Ctrl-P] Print
• [Ctrl-X] Close/Exit
• F1 Help

Graph Properties

The Graph Properties dialog allows you to modify all of the scaling and characteristics of the current graph.

Graph Property Control Buttons

• OK: Press OK to apply all of your changes to the current CurveExpert graph and quit the dialog.
• Apply: Press Apply to “try out” your graph property changes. The graph will be updated immediately, but you may still press Cancel to discard your changes.
• Apply to All: Press Apply to All to immediately apply all of the current graph properties to the current plot and all open plots. All attributes as well as the scaling for the current plot are copied to all other plots; hence, all graphs will have exactly the same view, colors, line thicknesses, etc. This action CANNOT be undone by pressing the Cancel button.
• Save as Default: If you would like to save your graph attribute and scaling setup permanently, click this button. This information will then be used on every plot that is drawn by CurveExpert.
• Cancel: Press Cancel to discard any changes that you have made to the graph properties and quit the dialog.
• Help: Press Help to get help on the currently selected tab of the Graph Properties dialog.
• Autoscale: Press this button to have CurveExpert automatically set the graph axes and tick mark increments. This is the default view for a newly opened graphing window, and ensures that all data points will be shown on the graphing window. This button is only available on the X and Y axis tabs.

If an invalid entry has been entered in any of the tabbed pages (for example, entering 0 for the Resolution parameter on the Overall page), then the offending entry will be selected, and the computers speaker will sound.

X and Y Axis Properties

The X axis and Y axis property sheets modify all graph properties that are associated with the x/y axes, such as the scaling, tick marks, and axis labels.

Scaling

Axis scaling is determined by the settings in the High and Low edit fields. As the names imply, the graph will be displayed over the range set by the Low value and the High value. Major tick marks will be placed at increments specified in the Increment edit field. Also, if the corresponding Show Grid Lines box is checked, grid lines will be displayed at each major tick. The number of minor ticks displayed between the major ticks is specified in the No. of Minors field.

Scale Type

The Scale Type section allows you to specify whether the axis should be scaled on a normal (linear) scale or a logarithmic scale. To use normal (linear) axes, select the Normal radio button. Likewise, to use logarithmic axes, select the Log radio button.

Using logarithmic scales has limitations – a plot showing zero or negative numbers on the axis in question cannot be scaled logarithmically. Of course, you can always reset the High and Low values to positive values to be able to scale the axis logarithmically. Note that the High, Low, and Increment fields are not represented exactly when using logarithmic scaling – the closest multiple of ten is chosen for the High and Low entered, and multiples of the next lower major tick are used for the minor increments.

Tick Labels

The tick labels for both axes can be customized by using the Tick Labels section of the Graph Properties dialog. The following options are available:

• Fixed Point: Select this radio button if you would like the numbers at every major tick to have fixed point format. The number of decimal places displayed is set in the Precision edit box below this radio button.
• Scientific: Select this radio button if you would like the numbers at every major tick to have a scientific/engineering format. The number of decimal places displayed is set in the Precision edit box below this radio button.
• Precision: The number in this field indicates the number of decimal places that will be displayed on the tick labels along the axes.
• Rotation: The tick labels can be rotated from 0 to 360 degrees. Enter the desired number of degrees to rotate these labels in the Rotation field.
• Font: The font used for the tick labels can be modified by clicking this button. Any Truetype font and any color can be chosen; refer to the Changing Graph Fonts section for details.

Miscellaneous

Axis properties that do not fall under one of the above categories are documented below.

• Label: Type in the axis label that is desired for the axis in question.
• Font: The font used for the axis label can be modified by clicking this button. Any Truetype font and any color can be chosen; refer to the Changing Graph Fonts section for details.
• Show Label: Select this checkbox if the axis label should be displayed. If this box is not checked, then the axis label will not be drawn.
• Show Grid Lines: Select this checkbox if grid lines (associated with the axis in question) should be shown at every major tick mark. If this box is not checked, then the grid lines will not be drawn.
• Grid Lines at Minors: Normally, grid lines are drawn only at the major ticks. Checking this button will cause the grid lines to be drawn at every minor tick also.
• Ticks Inside: Select this checkbox if all major and minor ticks should be drawn inside of the graph pane. If this box is not selected, all ticks will be drawn outside of the graph pane.

Point and Line Properties

The Point/Line property sheet modifies all graph properties associated with the appearance of the data point markers and the curve representing the model prediction.

Data Point Properties

• Show points: This checkbox will determine whether data points are drawn on the plot or not. For residual plots, this choice will read Show Residuals as Points. When this checkbox is selected, all residuals will appear as points on the graph. When left unselected, the residuals will be drawn as bars. Note that the properties of the residual points and/or bars can be controlled by the following properties, just as normal data points can.
• Fill points: This checkbox determines whether the points will be drawn as a solid color or an outline. For example, if the ‘circle’ symbol is chosen and the ‘Fill points’ options is checked, a solid disk will be drawn at each data point. The color used to fill the point is the same as the color used to draw the outline.
• Show Error Bars: This checkbox determines whether error bars will be shown on the data points, if standard deviation data is present in your data set. If this option is checked, then a rectangular error bar will be shown on each point. Note that this option will be disabled if your data set does not contain standard deviation data for each data point.
• Error Bar Scale: By default, the length of the error bar is the value of the standard deviation for the point is drawn on (this is unscaled, or scale=1.0). If you would like to scale the length of the error bar, then change the value of this item. A common use for this is to show a (theoretical) 95% confidence bound for the data point; this corresponds to a scale factor of 1.96, based on the Gaussian distribution. This item will not be enabled unless standard deviation data is present in the current data set.
• Point size: Enter the size of the symbol that will denote the data points, in pixels. This size may not be negative. The up/down buttons beside the edit control may also be used to change the size.
• Point color: The current point color is displayed beside this button. To change this color, press this button and choose a new color.
• Symbol: Press the ‘Symbol’ button to obtain a list of possible markers that can be used for each data point. The currently selected symbol will have a checkmark beside it on the symbol menu. Currently, the supported symbols are the circle, square, triangle, inverted triangle, hourglass, plus, and cross.

Line Properties

• Line Width: Enter the width, in pixels, of the curve that will be drawn as the curve fit. This size may not be negative. You may also use the up/down buttons beside the edit control to change the size. Note that the Line Width setting is only valid for solid lines; if any other style of line is chosen, then the width of the line will be one.
• Resolution: Enter the stepsize, in pixels, that the curve will be updated. The curve is made of straight line segments that appear as a curve when the resolution is small enough; however, the finer the resolution (lower number) the slower the curve will be drawn. For optimum performance, set the resolution to the highest number possible without degradation of plot quality.
• Line Color: The current line color is displayed beside this button. The line color is used to draw the curve fit line. To change this color, press this button and select a new color.
• Line Style: Press this button to display a menu with the available line types. Note that the Line Width setting is only valid for solid lines; if any other style of line is chosen, then the width of the line will be one.

Sample

This area of the Point/Line property dialog shows a sample of the currently selected point and line combination. Note that the background color is the currently selected Fill Color from the Overall tab. Also note that this sample is dynamically updated as you change the settings on this tabbed page.

Overall Graph Properties

The Overall property sheet modifies all properties associated with the plot as a whole, such as the title, graph pane, graph box, and graph coloring.

Show Header Instead of Title

Selecting this checkbox will display the header instead of the graph title. The header consists of the information button (which you can press to invoke the Information Dialog), directions concerning how to invoke the graphing menu, and the value of the standard error and the correlation coefficient for the current model. If this checkbox is left unselected, the title that is defined by the user in the Graph Title field will be centered in the window/page in the title font.

Graph Title

Enter the text for the graph title in this field. The string may be up to 255 characters long; if the title is too long for one line, then room will be made for it on the plot and it will broken up into multiple lines. Note that the title will not be displayed unless the Show Header Instead of Title checkbox (above) is left unselected.

Graph Title Font

Press this button to select a font for the title. See also Changing Graph Fonts for further details concerning how to use the font selection dialog.

Graph Pane

• Border Buttons: Select or deselect the pane border checkboxes to show or hide the lines around the graph pane.
• Lock Frame Color: If this button is checked, then all text drawn on the graph will automatically follow the selected Frame Color (see below). When this button is unchecked, the text colors can be individually selected through the Font selections in the Graph Properties dialog. Note that the text colors selected through the font dialogs will not be used unless this checkbox is unselected.
• Fill Color: The current fill color is displayed beside this button. The fill color is the color that will be used to shade in the background of the graph. To change this color, press this button and choose a new color.
• Grid Color: The current grid color is displayed beside this button. The grid color will be used to draw the dotted grid lines that are drawn at every major tick. To change this color, press this button and choose a new color.
• Frame Color: The current frame color is displayed beside this button. The frame color is used to draw the border around the graph as well as the tick marks. To change this color, press this button and choose a new color.
• Outside Fill: The current outside fill color is displayed beside this button. The outside fill color is the color that is painted outside of the graphing frame. Since the axes labels and various other printed items are drawn in this area, this color should not be the same as the Frame color. Remember that if the font color for the title, axes labels, etc. are the same color as the Outside Fill color, then they will be invisible! See the Lock Frame Color switch above for more information concerning this.

Graph Box

• Show Graph Box: To show or hide the graph box, select or deselect this checkbox, respectively. The graph box is the box that encloses the entire graph. This box is not very visible for on-screen plots; therefore, this option is most relevant for printed or copied plots.
• Box Width: Enter the line width, in pixels, that the graph box will be drawn with. Click the corresponding up/down arrows to increase or decrease this line width.
• Box Color: Click this button to select the color with which the graph box will be drawn.
• Rectangular Corners: Selecting this radio button will draw the graph box as a simple rectangle.
• Rounded Corners: Selecting this radio button will draw the graph box as a rectangle with rounded corners.

Graph Input and Output

Copy to Clipboard

Selecting this menu item copies the current plot to the clipboard so that you can paste it into another application. Best results when copying are obtained by resizing the graphing window to the actual size that you want to paste into the other application, and then selecting “Copy Plot.”

Print

Selecting this menu item prints a hardcopy of the current plot. A print dialog will be shown that will allow you to select printers and change the print setup. If the printer is not set as desired, press the Setup button and configure the printer. Pressing OK will commence printing, and pressing the Cancel button will return you to the CurveExpert graph window.

Note that you may select whether the printout will be in color or black and white by selecting the Black and White and Color radio buttons at the bottom of the dialog. If you have a black and white printer and select a color plot, then the plot will be grayscaled before it is sent to the printer.