Variable selection panel

These are the variable selection boxes, each of which is associated
with one variable, that is, one column of the input matrix.  The
variable selection boxes act as buttons which respond to mouse clicks
by selecting and 'deselecting' variables for plotting.  A selected
variable is indicated by a highlighted label in the corresponding
variable selection box.

Above the variable panel is a bit of text to remind the user of the
mouse actions to perform to select and deselect variables.  This
behavior depends on whether XGobi is in a two-variable plotting mode,
initiated by selecting XY Plot, a three-variable mode, initiated by
selecting Rotate, or in Tour, with three or more variables.

In XY Plot, a horizontal line is drawn in the variable circle of the X
variable and a vertical line in that of the Y variable.

In the three-variable mode, if "Y Axis" is selected, one Y variable is
plotted vertically against a linear combination of two X variables, and
the horizontal lines appearing in the variable circles are proportional
in length to the coefficients of the two X variables.  If "X Axis" is
selected, a linear combination of two variables rotates about the
horizontal axis in the plane of the screen; now the vertical lines are
proportional in length to the coefficients of the Y variables.

In Tour mode, the lines in the variable circles are oblique, and
provide information about the magnitude and direction of the
contribution of each variable. The circle interior to one of the
variable circles indicates that this variable is available for manual
manipulation (see help under the Manip menu for more information on
variable manipulation). It is also possible to "freeze" a variable's
contribution to the tour, and when frozen the variable circle has a
smaller dashed interior circle.

In Corr mode, the lines in the variable circles are horizontal or
vertical, indicating the magnitude of the contribution of the variable
to either horizontal or vertical directions in the plot. The small
arcs interior to the variable circles indicate variables available for
manipulation. Arcs at top and bottom mean that the variable's
contribution can be manipulated vertically, and arcs at left and right
indicate that horizontal manipulation. It is also possible to "freeze"
a variable's contribution to the tour, and when frozen the variable
circle has a smaller dashed interior arc.


Here is a more detailed description of the selection behavior in each
of the three modes.

One-variable plotting, initiated as Plot1D:

  Click
   the active variable    if making textured dot plots, generate a new
                          plot for this variable
   an inactive variable   this variable replaces the active variable

  If the click is a left click, plot horizontally; if a middle
  click, plot vertically.

Two-variable plotting, initiated as XYPlot:

  Left click
   an inactive variable    this variable replaces the active X
   the active Y variable   X and Y are exchanged

  Middle click
   an inactive variable    this variable replaces the active Y
   the active X variable   X and Y are exchanged

Three-variable plotting, initiated as Rotate:

 In this mode, we use the idea that a variable can be the
 "last touched," and then it is targeted for replacement.  The
 "last touched" variable is indicated with a small circle in the
 center of its variable circle, suggesting a target.

 Y axis:

  Here, only the horizontally plotted variables can be
  last_touched.

  Left click
   an X variable           this variable becomes the last touched
   an inactive variable    replaces the last touched X
   the active Y variable   is exchanged with the last touched X

  Middle click
   an inactive variable    this variable replaces Y
   an X variable           the selected X is exchanged with Y

 X axis:

  Here, only the vertically plotted variables can be
  last_touched.

  Left click
   an inactive variable    this variable replaces X
   a Y variable            the selected Y is exchanged with X     

  Middle click
   a Y variable            this variables becomes the last touched
   an inactive variable    replaces the last touched Y
   the active X variable   is exchanged with the last touched Y

 Oblique axis:

  Any click
   an active variable      becomes last touched
   an inactive variable    replaces the last touched variable

Tour:

  Left or middle click:
   an inactive variable    this variable becomes part of the next basis
   an active variable      this variable is removed from the next basis
  Holding Shift with a left or middle click:
   the manip variable      nothing
   any other variable      this variable becomes the manip variable
  Holding Ctrl with a left or middle click:
   a frozen variable       unfreezes this variable, so its contribution
                           to the tour is unrestricted
   any other ACTIVE var    this variable's contribution becomes frozen

Corr:

  Left click:
   active X variable       this variable is removed from the next basis
                             unless it is the only active X variable
   inactive variable       this variable is added the the active X list
   active Y variable       this variable is removed from the active Y
                             list and added to the active X list
  Middle click:
   active Y variable       this variable is removed from the next basis
                             unless it is the only active Y variable
   inactive variable       this variable is added the the active Y list
   active X variable       this variable is removed from the active X
                             list and added to the active Y list
 Holding Shift with left click:
   X manip variable        nothing
   any other variable      this variable becomes the X manip variable
 Holding Shift with right click:
   Y manip variable        nothing
   any other variable      this variable becomes the Y manip variable

 Holding Ctrl with a left click:
   a frozen X variable     unfreezes this variable, so its contribution
                           to the horizontal is unrestricted
   any ACTIVE X var        this variable's contribution horizontally 
                           becomes frozen
 Holding Ctrl with a middle click:
   a frozen Y variable     unfreezes this variable, so its contribution
                           to the vertical is unrestricted
   any ACTIVE Y var        this variable's contribution vertically 
                           becomes frozen

The partitioning of the space between the control panels, the plot
window, the variable selection panel can be made by positioning the
cursor above the little rectangles (called grips) that are at the
bottom of the lines separating these regions, then pressing one of the
mouse buttons and moving the cursor to the left or right.  If this
still doesn't result in a good division of space between the plot
window and the variable selection panel, you might want to adjust
the height and width of PlotWindow or VarPanel using your XGobi
resource file.

Of special interest are these resources:

To set the width of the entire panel:
    *XGobi*VarPanel.width: 200

To set the width of the variable circles:
    *XGobi*VarLabel.width: 34
    *XGobi*VarWindow.width: 34

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