The Control bar
- Overview: The Control bar both changes and
displays the current axis, subsample rate and zoom factor.
- Axis:
The axis symbol shows the current orientation of the axis. Clicking the axis
symbol rotates the axis. Each left click rotates
the axis counter-clockwise 90 degrees. Each right click rotates the
axis clockwise 90 degrees.
- Subsample:
The subsample factor determines the fraction of data points in the file
that are displayed. If the subsample factor is one, every data points is
displayed. If the subsample factor is ten, every tenth data point is displayed.
A higher subsample factor allows faster browsing.
- Changing the Subsample factor:
Two techniques using the control bar can be used to change the
subsample factor. The first technique is to move the top
scale bar
until the subsample factor is the desired value.
The second technique is to simply left-click
on the number to the right of subsample:. The desired subsample
factor can then be typed in.
The subsample factor can also be changed using the
keyboard.
- ZOOM:
The zoom controls the magnification of the vector display. Assuming no
other changes, increasing the zoom factor results in a smaller region of data
displayed in the same size window with a corresponding increase in arrow size.
However the size of the arrow, as discussed below, depends also on the
subsample rate and the size of the frame. The zoom factor is the number
of pixels in the frame divided by the number of arrows in the frame
assuming the subsample rate is one. When the subsample rate is
increased from one, the number of arrows is decreased and the number
of pixels available to each arrow is increased causing an increase in
the arrow's size. Thus the subsample rate also effects the size of
the arrows but in away independent of the zoom factor. The subsample
rate corresponds to the resolution of the display while the zoom
factor corresponds to the closeness to the display.
- Changing the Zoom level:
Two techniques using the control bar, one technique using the
keyboard,
and one technique that works by
outlining an area in the display window,
can be used to change the zoom level.
The first technique is to move the bottom
scale bar
until the subsample factor is the desired value.
The second technique is to simply left-click on
the number to the right of Zoom:. The desired zoom value can then
be typed in. A menu command,
Fill Display ,
can also change the zoom level.
- Turning Off:
The control bar may be turned off by toggling the
control bar option off under the option menu.
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