205 lines
5.1 KiB
Plaintext
205 lines
5.1 KiB
Plaintext
.TH GVIEW 1
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.SH NAME
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gview \- interactive graph viewer
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.SH SYNOPSIS
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.B gview
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[
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.B -mp
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]
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[
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.B -l
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.I logfile
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]
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[
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.I files
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]
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.SH DESCRIPTION
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.I Gview
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reads polygonal lines or a polygonal line drawing from an
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.B ASCII
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input file (which defaults to standard input), and views it interactively,
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with commands to zoom in and out, perform simple editing operations, and
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display information about points and polylines. (Multiple input files are
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allowed if you want to overlay several line drawings.) The editing commands can
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change the color and thickness of the polylines, delete (or undelete)
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some of them, and optionally rotate and move them. It is also possible to
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generate an output file that reflects these changes and is in the same format
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as the input.
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.PP
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Since the
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.B move
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and
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.B rotate
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commands are undesirable when just viewing a graph, they are only enabled if
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.I gview
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is invoked with the
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.B -m
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option.
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.PP
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The
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.B -p
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option plots only the vertices of the polygons.
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.PP
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Clicking on a polyline with button 1 displays the coordinates and a
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.I t
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value that tells how far along the polyline.
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.IR (t =0
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at the first vertex,
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.IR t =1
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at the first vertex,
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.IR t =1.5
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halfway between the second and third vertices, etc.) The
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.B -l
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option generates a log file that lists all points selected in this manner.
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.PP
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The most important interactive operations are to
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.I zoom in
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by sweeping out a rectangle, or to
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.I zoom out
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so that everything currently being displayed shrinks to fit in the swept-out
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rectangle. Other options on the button 3 menu are
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.I unzoom
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which restores the coordinate system to the default state where everything
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fits on the screen,
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.I recenter
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which takes a point and makes it the center of the window, and
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.I square up
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which makes the horizontal and vertical scale factors equal.
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.PP
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To take a graph of a function where some part is almost linear and
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see how it deviates from a straight line, select two points on this
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part of the graph (i.e., select one with button 1 and then select the
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other) and then use the
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.I slant
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command on the button 3 menu.
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This slants the coordinate system so that the line between the two
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selected points appears horizontal (but vertical still means positive
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.IR y ).
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Then the
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.I zoom in
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command can be used to accentuate deviations from horizontal.
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There is also an
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.I unslant
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command that undoes all of this and goes back to an unslanted coordinate
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system.
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.PP
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There is a
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.I recolor
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command on button 3 that lets you select a color and change everything
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to have that color, and a similar command on button 2 that only affects
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the selected polyline. If the input file uses the
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.B Multi(...)
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feature explained below, either flavor of
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.I recolor
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allows you to type a digit in lieu of selecting a color.
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.PP
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The
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.I thick
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or
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.I thin
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command on button 2 changes the thickness of the selected polyline
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and there is also an undo command for such edits.
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Finally, button 3 has commands to
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.I read
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a new input file and display it on top of everything else,
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.I restack
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the drawing order (in case lines of different color are drawn on top of
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each other),
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.I write
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everything into an output file, or
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.I exit
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the program.
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.PP
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Each polyline in an input or output file is a space-delimited
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.I x
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.I y
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coordinate pair on a line by itself, and the polyline is a sequence
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of such vertices followed by a label. The label could be just a
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blank line or it could be a string in double
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quotes, or virtually any text that does not contain spaces and is
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on a line by itself. The label at the end of the last polyline is
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optional. It is not legal to have two consecutive labels, since that
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would denote a zero-vertex polyline and each polyline must have at least
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one vertex. (One-vertex polylines are useful for scatter plots.)
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Under the
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.B -l
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option, a newline causes the selected polyline's label to appear in
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the log file (where it could be seen by invoking
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.B tail -f
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in another window).
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If the label after a polyline contains the word
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.B "Thick"
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or a color name
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.BR (Red ,
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.BR Pink ,
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.BR Dkred ,
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.BR Orange ,
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.BR Yellow ,
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.BR Dkyellow ,
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.BR Green ,
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.BR Dkgreen ,
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.BR Cyan ,
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.BR Blue ,
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.BR Ltblue ,
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.BR Magenta ,
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.BR Violet ,
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.BR Gray ,
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.BR Black ,
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.BR White ),
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whichever color name comes first will be used to color the polyline.
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Alternatively, labels can contain
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.B Multi
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followed by single-letter versions of these names:
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.BR (R ,
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.BR P ,
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.BR r ,
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.BR O ,
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.BR Y ,
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.BR y ,
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.BR G ,
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.BR g ,
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.BR C ,
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.BR B ,
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.BR b ,
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.BR M ,
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.BR V ,
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.BR A ,
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.BR K ,
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.BR W ,
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each optionally preceded by
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.BR T ).
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Then
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.I recolor
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followed by a nonzero digit
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.I n
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selects the
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.IR n th
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alternative for each polyline.
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.SH EXAMPLE
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To see a graph of the function
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.IR y = sin( x )/ x ,
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generate input with an awk script and pipe it into
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.IR gview :
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.IP
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.EX
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awk 'BEGIN{for(x=.1;x<500;x+=.1)print x,sin(x)/x}' | gview
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.EE
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.SH SOURCE
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.B /sys/src/cmd/gview.c
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.SH SEE ALSO
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.IR awk (1),
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.IR tail (1)
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.SH BUGS
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The user interface for the
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.I slant
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command is counter-intuitive. Perhaps it would be better to have a scheme
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for sweeping out a parallelogram.
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.PP
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The
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.B -p
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option makes the interactive point selection feature behave strangely, and
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is unnecessary since extra blank lines in the input achieve essentially the
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same effect.
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