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<title>gview(1) - Plan 9 from User Space</title>
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<tr><td width=20><td><b>GVIEW(1)</b><td align=right><b>GVIEW(1)</b>
<tr><td width=20><td colspan=2>
<br>
<p><font size=+1><b>NAME </b></font><br>
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gview – interactive graph viewer<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>gview</font></tt> [ <tt><font size=+1>−l</font></tt> <i>logfile</i> ] [ <tt><font size=+1>−m</font></tt> ] [ <i>file</i> ]<br>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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<i>Gview</i> reads polygonal lines or a polygonal line drawing from an
<tt><font size=+1>ASCII</font></tt> input file (which defaults to standard input), and views
it interactively, with commands to zoom in and out, perform simple
editing operations, and display information about points and polylines.
The editing commands can change the color and
thickness of the polylines, delete (or undelete) some of them,
and optionally rotate and move them. It is also possible to generate
an output file that reflects these changes and is in the same
format as the input.
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Since the <tt><font size=+1>move</font></tt> and <tt><font size=+1>rotate</font></tt> commands are undesirable when just viewing
a graph, they are only enabled if <i>gview</i> is invoked with the <tt><font size=+1>−m</font></tt>
option.
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Clicking on a polyline with button 1 displays the coordinates
and a <i>t</i> value that tells how far along the polyline. <i>(t</i>=0 at the
first vertex, <i>t</i>=1 at the first vertex, <i>t</i>=1.5 halfway between the
second and third vertices, etc.) The <tt><font size=+1>−l</font></tt> option generates a log
file that lists all points selected in this manner.
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The most important interactive operations are to <i>zoom in</i> by sweeping
out a rectangle, or to <i>zoom out</i> so that everything currently being
displayed shrinks to fit in the swept-out rectangle. Other options
on the button 3 menu are <i>unzoom</i> which restores the coordinate
system to the default state where everything fits on
the screen, <i>recenter</i> which takes a point and makes it the center
of the window, and <i>square up</i> which makes the horizontal and vertical
scale factors equal.
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To take a graph of a function where some part is almost linear
and see how it deviates from a straight line, select two points
on this part of the graph (i.e., select one with button 1 and
then select the other) and then use the <i>slant</i> command on the button
3 menu. This slants the coordinate system so that the line
between the two selected points appears horizontal (but vertical
still means positive <i>y</i>). Then the <i>zoom in</i> command can be used
to accentuate deviations from horizontal. There is also an <i>unslant</i>
command that undoes all of this and goes back to an unslanted
coordinate system.
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There is a <i>recolor</i> command on button 3 that lets you select a
color and change everything to have that color, and a similar
command on button 2 that only affects the selected polyline. The
<i>thick</i> or <i>thin</i> command on button 2 changes the thickness of the
selected polyline and there is also an undo command for such
edits.
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Finally, button 3 had commands to <i>read</i> a new input file and display
it on top of everything else, <i>restack</i> the drawing order (in case
lines of different color are drawn on top of each other), <i>write</i>
everything into an output file, or <i>exit</i> the program.
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Each polyline in an input or output file is a space-delimited
<i>x y</i> coordinate pair on a line by itself, and the polyline is a
sequence of such vertices followed by a label. The label could
be just a blank line or it could be a string in double quotes,
or virtually any text that does not contain spaces and is on a
line by itself. The
label at the end of the last polyline is optional. It is not legal
to have two consecutive labels, since that would denote a zero-vertex
polyline and each polyline must have at least one vertex. (One-vertex
polylines are useful for scatter plots.)<br>
If the label after a polyline can contains the word <tt><font size=+1>Thick</font></tt> or a
color name <tt><font size=+1>(Red</font></tt>, <tt><font size=+1>Pink</font></tt>, <tt><font size=+1>Dkred</font></tt>, <tt><font size=+1>Orange</font></tt>, <tt><font size=+1>Yellow</font></tt>, <tt><font size=+1>Dkyellow</font></tt>, <tt><font size=+1>Green</font></tt>,
<tt><font size=+1>Dkgreen</font></tt>, <tt><font size=+1>Cyan</font></tt>, <tt><font size=+1>Blue</font></tt>, <tt><font size=+1>Ltblue</font></tt>, <tt><font size=+1>Magenta</font></tt>, <tt><font size=+1>Violet</font></tt>, <tt><font size=+1>Gray</font></tt>, <tt><font size=+1>Black</font></tt>, <tt><font size=+1>White</font></tt>),
whichever color name comes first will be used to color the polyline.
</table>
<p><font size=+1><b>EXAMPLE </b></font><br>
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To see a graph of the function <i>y</i>=<i>sin(</i>x<i>)/</i>x generate input with
an awk script and pipe it into <i>gview</i>:<br>
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<tt><font size=+1>awk 'BEGIN{for(x=.1;x<500;x+=.1)print x,sin(x)/x}' | gview<br>
</font></tt>
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<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/cmd/draw/gview.c<br>
</font></tt>
</table>
<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man1/awk.html"><i>awk</i>(1)</a><br>
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<p><font size=+1><b>BUGS </b></font><br>
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The user interface for the <i>slant</i> command is counter-intuitive.
Perhaps it would be better to have a scheme for sweeping out a
parallelogram.<br>
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