Brush

This activates a set of operations used in brushing.  Brushing can be
performed with one single XGobi process running, but it is most
interesting and useful to perform brushing with more than one XGobi
process active at the same time, with a different view of the same data
displayed in each.  When brushing operations are performed in any one
XGobi window, the new current state is instantly broadcast.  Any other
XGobi window that read the broadcast information promptly updates its
own window to reflect the changes.  In order to respond to brushing
events, an XGobi process must be plotting data with the same number of
rows as the broadcasting window, but it need not be in the Brushing
mode itself.  (In fact, machine response is best if the passive window
is in a Pause state or in the XY Plot mode, consuming few computing
cycles.)  In order to prevent the sending or receiving of brushing
information, select Unlink in the main panel.

The instruction label that appears above the plotting window is
there to remind you of the brush use.  As you move the pointer
inside the plotting window, the "brush," which is drawn in the
current plotting color, will move with you.  If you are brushing
points, the brush is a rectangle and points contained inside it
are brushed; if you are brushing line segments, the brush is a
crosshair and line segments intersected by either leg of the
brush are brushed.  It is possible to brush both points and line
segments at the same time.

To brush points or lines, hold the left button down and move the
pointer.  To reshape the brush, hold down the middle button and 
move.  To brush and reshape at the same time, hold down both the
left and middle buttons.

This button can be activated from the keyboard by typing b or B.
