View Menu

Every element in the view menu changes two things:
  1) the interactions defined for the plot window, and
  2) the panel displayed to the left of the plotting window.

The elements in top half of the menu in general change the
dimensionality of the projection in the plotting window, while
those in the bottom half do not.

DotPlot

A one-variable plotting mode, displaying the data in a vertical strip
chart, like a jittered dot plot.  The method used is described in
"Strips Displaying Empirical Distributions:  I.  Textured Dot Strips"
by John Tukey and Paul Tukey.

Only the middle button is effective in this mode.  See the help file
for the variable selection panel for more detail.

This view can be activated from the keyboard by typing d or D.

XYPlot

The familiar two-variable scatterplot ...

A horizontal line is drawn in the variable circle corresponding to the
X variable plotted and a vertical line in that of the Y variable.  See
the help file for the variable selection panel for more information.

These plots can be cycled automatically:  see the help file for the
Cycle button in the XYPlot control panel.

This view can be activated from the keyboard by typing x or X.

Rotate

Selecting Rotate sets XGobi in a three-variable plotting mode.  The
user can rotate the data about a fixed vertical or horizontal axis, or
about a floating oblique axis, which is controlled by mouse movements
on the screen.

To control the rotation with mouse movements, press and hold any mouse
button while the cursor is in the plotting window.  Now move the
cursor.  (Note that when the axis is fixed, movement is possible around
that axis.)

The lines appearing in the variable circles are proportional in length
and direction to the axes of the three participating variables, and the
small circle in the center of the variable circle indicates that a
variable is "last touched." See the help file for the variable
selection panel for more detail.

If there are fewer than three variables in the data, rotation is
disabled.

This view can be activated from the keyboard by typing r or R.

Grand Tour: grand tour and projection pursuit guided tour

Initiate a grand tour using the first three variables in the data
matrix.  The labels of the included variables are highlighted.  (If
there are fewer than three variables in the data, motion ceases.)

The grand tour method used here successively samples planes in p-space,
where p is the number of variables presently selected, and connects the
planes by moving along a geodesic interpolation path between them.
Motion is smooth between the starting and ending planes, but when the
ending plane is reached there is a slight delay while the next randomly
selected ending plane and consequent path are calculated.  By allowing
the grand tour to run uninterrupted the viewer can get a global view of
the linear combinations among the variables. As the tour runs, the
number of base planes passed is displayed in the box to the right of
the Backtrack button.

A variable may be added to or removed from the tour by clicking on the
corresponding variable selection box with the left or middle mouse
button.  There must be three or more variables included in the grand
tour, so it is not possible to remove a variable when only three are
active. The bars drawn inside the variable circles represent the
coefficients of the variables in the current plot.  The projection of a
bar on the horizontal axis of the variable circle corresponds to the X
coefficient of that variable, while the projection onto the vertical
axis of the variable circle corresponds to the Y coefficient.

This view can be activated from the keyboard by typing t or T.

Correlation Tour

Initiate a correlation (alias regression or canonical) tour with
the first variable as the "dependent" vertical variable and the second
two variables as "independent" horizontal variables. See Buja, Hurley,
Asimov and McDonald "Elements of a Viewing Pipeline" in Cleveland and
McGill (1989?) "Dynamic Graphics for Statistics".

Variables are added or removed with either a left or middle button
click. Left for X variable, Middle for Y variable. When removed the
variable will be faded out. To change from an X variable to a Y
variable one needs to click on the variable circle with the middle
button, and when the X component is faded out the Y component is
introduced. Vice versa for changing a Y to an X. 

Set this view from the keyboard by pressing c or C.

Scale

Activate a set of operations for scaling and shifting the data inside
the plotting window.  The first set of controls in the scale panel
applies to rescaling operations, and the second set to operations
that shift the center of the data.

It is also possible to scale and shift the data using mouse operations
inside the plotting window.  XGobi signals these changes in two ways:
The cursor changes inside the plotting window and a bit of text appears
above the window to briefly describe the mouse behavior.  You can shift
the plot by dragging left and rescale it by dragging middle.  If that
sentence is too terse for you, read the following paragraph:

 Place the cursor inside the plotting window.  Now hold the left button
 down while moving the mouse, and notice that the plot moves around
 inside the plotting region without changing shape.  Now try doing the
 same with the middle button, and notice that the plot is continuously
 being rescaled.

Activate this view from the keyboard by typing s or S.

Brush

Activate 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.

Active this view from the keyboard by typing b or B.

Identify

This mode is used to identify the case (row) of plotted points.  If
a file containing case labels has been supplied, those labels are
used here.  If not, the row number of each point is used.  To see
these labels, simply move the cursor inside the plotting window.
The label of the point nearest the cursor will be printed.

To cause a label to become "sticky", click left when the target
label is printed.  The printing style changes and the label now
remains printed as the cursor moves off, and even remains printed
as you leave the Identify mode.  It is possible to rescale or
rotate data, and the sticky labels will continue to be printed next
to their associated points.

To cause a label to become "unsticky", return to the Identify mode
and click left again when the target point is nearest the cursor.

Identification works in a single window or in one or more linked
windows.

This button can be activated from the keyboard by typing i or I.

Row labels can be supplied in a file named fname.row, where fname
or fname.data is the name of the data file, one label per row.

LineEdit

This element enables an interactive line editor, allows line
segments between points to be added or removed interactively.
When you select LineEdit, if the connecting lines are not
currently being shown, the "Show lines" option is turned on
and the connecting lines are plotted.
(See the help file for the Options button in the main panel.)

The connecting lines can be specified in a startup file named using a
.lines suffix.  The .lines file consists of pairs of numbers on
separate lines, where the pair indicates the row numbers of the
points to be connected, for example:

1 3
1 4
2 5

Line colors can be supplied in a file named fname.linecolors,
where fname or fname.data is the name of the data file, one
color per row, where the rows correspond to the rows specified
in the .lines file.

Activate line editing from the keyboard by typing l or L.

Move points

Drag the left mouse button to move points in the plot window.
In non-orthogonal projections, point motion is taken as occurring
in a plane parallel to the plane of the screen.

Activate point moving from the keyboard by typing m or M.