The Plotter
Siag uses Gnuplot for plotting. Gnuplot is normally used interactively,
that is, commands are entered on the command line. When used from Siag,
however, Siag automatically
produces data and command files which are then processed
by Gnuplot, so that it is not necessary to learn any Gnuplot commands
to produce graphs from Siag.
Gnuplot Made Easy
To produce a graph from Siag, do the following:
- Set the block on the data you want to plot
- Click on the plotting icon
That's it. This will produce a graph using lines. If the top row
in the block contains labels, these will automatically be used
for tic marks on the x axis. If the leftmost column contains
labels, these will automatically be used as titles for the graphs.
Anything else is used as data with one dataset per line.
The Plot menu can be used to select other plot styles. These are
available:
- Lines
- Connects adjacent lines with points.
- Points
- Displays a small symbol at each point.
- Linespoints
- The linespoints style does both lines and points.
- Impulses
- Displays a vertical line from the x axis
to each point.
- Dots
- Plots a tiny dot at each point.
- Steps
- This style connects consecutive points with two
line segments: the first from (x1,y1) to (x1,y2)
and the second from (x1,y2) to (x2,y2).
- Boxes
- The boxes style draws
a box centered about the yaxis to the given y
coordinate.
Advanced Plotting
None of this is actually implemented yet. This only describes
what I would eventually be able to do with Siag.
The "Advanced" plotting mode is only for users who are familiar with
Gnuplot and the inner workings of Siag. It provides the possibility
to plot anything that Gnuplot can plot, including 3D plots
and plots where different datasets use different styles. The cost
of this flexibility is that the plotting commands have to be entered
as text.
The description below comes from the on-line help in Gnuplot.
While the numerous parameters may seem intimidating, reasonable
defaults are available for everything.
- mode
- The two primary plotting modes are 2D and 3D.
- title
- A title of each plot appears in the key
- style
- Plots may be displayed in one of eight styles:
- lines
- Connects adjacent lines with points.
- points
- Displays a small symbol at each point.
- linespoints
- The linespoints style does both lines and points.
- impulses
- Displays a vertical line from the x axis
(or from the grid base for 3D plots) to each point.
- dots
- Plots a tiny dot at each point.
- errorbars
- The errorbars style is only relevant for 2D plotting.
It is like points, except that a vertical error bar
is also drawn from (x,ylow) to (x,yhigh). A tic
mark is placed at the ends of the error bar.
- steps
- This style connects consecutive points with two
line segments: the first from (x1,y1) to (x1,y2)
and the second from (x1,y2) to (x2,y2).
- boxes
- The boxes style is only relevant to 2D plotting. It draws
a box centered about the yaxis to the given y
coordinate.
- boxerrorbars
- This style is a combination is combination of the boxes
and errorbars styles.
- labels
- The x- and y-axis have lables. The x label is centered
along the x axis and the position of the y label depends
on the terminal.
- terminal
- Selects the type of graphics device for which Gnuplot
will produce output.
- output
- Directs the display to the specified file or device.
- logscale
- Log scaling may be set on the x, y, and z axes. Any combination
of x, y and z axes may use log scaling. If the base is not set,
10 is assumed.
- tics
- Fine control of the axis tic marks is possible. See the
documentation that comes with Gnuplot for more on this.
- grid
- If this is selected, a grid is drawn at the tic marks.
- time
- If selected, the time and date of the plot is placed
at the top or bottom of the left margin. The exact location
is device dependent.
- size
- Scales the displayed size of the plot.
Ulric Eriksson - January 1997 - ulric@siag.nu