Trace curve mode

To automatically trace points on a curve in your graph, you must make sure you are in Trace curve mode. You can select Trace curve mode from the Edit menu, or from the mode selection in the top left of the window.

You can only enter Trace curve mode if your axes have been defined.

You can trace both solid and dashed curves, although the result may be better for solid curves. You can trace intersecting curves, but the curves must not fold back on themselves; there must be a single X value for each Y, or vice versa. The color and thickness of your curve are important pieces of information. Therefore, if your graph was in color, make sure you scan or import it in color, and at an appropriate resolution.

Before you start, make sure the scan window size is set appropriate. The scan window size (in pixels) defines the distance ScanIt looks around to recognize the curve. You can set it in the top of the window, under the mode selection list. Your curve properties such as thickness, pattern, etc. should easily fit in the scan window. You can check this in the Zoom View that will show your scan window as a box around the mouse position. If tracing stops at gaps, increase the window size.

To start tracing a curve, click on or near a well-defined part of it. The point you have clicked will first be snapped to the curve. See Manual pick mode for a description of Snap. If Snap fails, you have clicked too far from a curve to be able to trace it.

You will be asked for the direction of your curve. This is either in X or Y direction, positive or negative. Make sure that if you select the X direction, only one Y value exists for each X, and vice versa. If the beginning of your curve is fuzzy or unclear, click on the end of the curve and trace in the opposite direction.

The tracing algorithm is recursive. You may get better results at the expense of a longer wait. See options for the details.

You can abort tracing by pressing Esc.

Often, the tracer tends to make up a few points at the end of your curve. Remove those by pressing Ctrl+Backspace.

The traced points will show as symbols on your screen. Selected data points appear in another color than unselected data points (see options). As long as your data is visible, you can select and manipulate your data.

Press Ctrl+L to toggle connecting your data points with lines.

See also: Defining your axes, Manual pick mode, Scan for symbols mode.