The Plot display provides 2D plots of change in the values of data points versus time, or 2D parametric plots of data point values versus other values. It handles double, integer and matrix values; for matrices, it operates on a per-element basis. A simple plot display may have several distinct plots within it; for instance, the three elements of a position matrix may be displayed in three vertically arranged displays.
To create a Plot display, drag the plot from the Tools window onto an open area of an interface page. The initial plot will appear without drawing anything except for the default border and background; this is normal. When a data point is dropped from the Data Tree onto the plot, a Data View will be created within the plot and the time history of the data point will begin to be displayed. Subsequent points dropped onto the display will add additional lines to the plot; the color of each point will be shown in a legend to the bottom left of the plot. A matrix dropped onto the plot will create a separate line for each element of the matrix.
Each Data View within the plot display can be independently panned and zoomed. Associated with such control is the view stack, allowing the user to back out from a certain zoom level to the previous view of the data. When the plot is first created, the Data View is at the base of the stack, where the axis of the plot will expand (or move to follow, see configuration below) new incoming data values.Whenever the data view is at the base of the stack (actively resizing for or following data) panning in addition to zooming will create a new stack frame. When the current stack frame is not the base frame, only zooming will create a new stack frame. To pan the graph, the user need only click and drag on the data view. To zoom, hold down the shift key and then click and drag to define the rectangle to zoom to. To return to the previous stack frame, the user may double-click anywhere within the data view; to return all the way to the base stack frame, the user may triple-click anywhere within the data view.
At the top left of the Data View within the display (once at least one point has been dropped onto the display) is a square marked with a small '+'. Clicking this button reveals or hides a small menu of options across the top of the data view. The exact options presented will depend on whether or not the current stack frame is the base frame (that is, currently resizing or following incoming data rather than having been panned or zoomed).
If the plot has been panned or zoomed and is consequently not at the base frame, the options available within the + menu are simple.
The options available when the plot is currently at its base frame are slightly more complicated.
The Plot display provides extensive configuration options. The following section will describe these options in detail.
The Plot configuration window is divided into three sections:
The topmost set of controls within the configuration window apply to the plot display as a whole rather than to individual plot views. There are four color controls, allowing selection of the graph's background color, the color of all text drawn within the display, and the colors of the major and minor tick lines drawn on the graphs. Transparent and semi-transparent colors can be chosen here, but the transparency will have no effect for the graph background. Along with the four color selections, the "Darken Plot Views" checkbox turns on a small darkening of the area around each individual plot view that serves to better visually set off individual plot views within the display.
In addition to color control, the font and size of text drawn in the display can be chosen. The display will scale plot margins to ensure that text will have sufficient space regardless of the chosen font and size.
A plot display is broken up into some number of individual plot views. The central section of the configuration window allows each plot view to be configured; the "View:" popup menu selects which plot view is currently being examined. The "Label:" field allows the currently selected plot view to be given a new label. Below these two controls, the configuration of the plot view is broken up into two sections, one for each axis of the plot.
The Y-Axis configuration box is fairly straightforward, containing only three controls. The "Tick Field Width:" control in the upper right is the simplest, merely controling the number of digits for which the Y-Axis margin is sized to display. Changing the number here will dynamically alter the left margin so that the appropriate number of digits can be displayed in the chosen font and font size.
The "Resize for incoming data" and "Resize can shrink" checkboxes affect whether or not the scale of the Y-Axis will be resized to accomodate new incoming data when the view is at the base of the view stack (see above.) The first allows the Y-Axis to grow larger as necessary; the second allows the Y-Axis to grow smaller when the possible if the view is in Follow mode.
The first control within the X-Axis configuration box simply allows a custom label to be specified. When the checkbox is on and a label is entered, the label will appear beneath the X-Axis rather than the tiem resolution string or, in parametric mode, the name of the parametric input.
Within the X-Axis configuration box there are also controls for affecting the automatic resizing of the axis. However, while the "Resize for incoming data" control also allows the axis to expand to contain the new data, the "Follow can shrink" control is enabled only when the plot view is in Parametric mode (see below) with Follow on. In this case, it acts in the same fashion as the Y-Axis "Resize can shrink", allowing the axis to shrink when the scale of displayed data permits. The "Follow incoming data" control turns on and off Follow mode for the view just as the in-view menu button does; in the configuration box, however, the "Distance (sec)" box allows the number of seconds' worth of data that is displayed to be configured.
The most important control within the X-Axis configuration box is the checkbox labeled "Parametric on:" and the associated popup button. When this button is not checked, the plot view is in "normal" mode, with each associated input plotted against time on the X axis. Checking this box and selecting an input element, however, puts the display into parametric mode. In this mode, all inputs other than the parametric input are plotted versus the value, along the X-Axis, of the parametric input at the same time. When selecting the parametric input, ensure that the selected input is "Active" in the table at the bottom of the window (see below) or unexpected results may occur.
The bottom portion of the configuration window controls which input elements are active, the color of their lines, and which plot views they are assigned to. This is controlled by the table of input elements. Color can be changed by clicking on the color well for the element you wish to change and selecting the appropriate color. The Active checkbox turns on and off display of individual elements; if an element is not Active, it will not be displayed, regardless of the plot view to which it is assigned.
The View column allows each element to be assigned to a specific plot view; the popup menu allows the selected view to be changed. The views are numbered starting at 0 for the topmost view.
The "+", "-" and "Condense" buttons control plot view creation and destruction. The "+" button will create a new plot view to which elements can then be assigned. The "-" will remove the highest-numbered (bottommost displayed) plot view; any elements assigned to the removed plot view will be reassigned to view 0. The "Condense" button removes all plot views except for view 0, and reassigns all input elements to that plot view.