Q: How to plot col(A):col(B) if col(C) == 0?
A: plot ‘dataset.txt’ using 1:($3==0?$2:1/0)

Q: What if we want to plot conditionally on another column containing text?
A: plot ‘dataset.txt’ using 1:(stringcolumn(3) eq “a”? $2:1/0) title “a” lc rgb “blue” ,\ “” using 1:(stringcolumn(3) eq “b”? $2:1/0) title “b” lc rgb “red”

Q: What is ‘stats’?
Syntax:
stats 'filename' [using N[:M]] [name 'prefix'] [[no]output]]
Example:
stats "dataset.txt" using 2 name "A"

Q: How to draw a rectangle with a colored border in gnuplot?
Syntax:
set object <index> rectangle
           {from <position> {to|rto} <position> |
           center <position> size <w>,<h> |
           at <position> size <w>,<h>}

# Force the entire area enclosed by the axes to have background color cyan
set object 1 rect from graph 0, graph 0 to graph 1, graph 1 back
set object 1 rect fc rgb "cyan" fillstyle solid 1.0

# Position a red square with lower left at 0,0 and upper right at 2,3
set object 2 rect from 0,0 to 2,3 fc lt 1
     
# Position an empty rectangle (no fill) with a blue border
set object 3 rect from 0,0 to 2,3 fs empty border rgb "blue"
     
# Return fill and color to the default style but leave vertices unchanged
set object 2 rect default

timecolumn() function parses a time string from a column according to the set timefmt settings. The result is a time stamp in seconds.

set xdata time 
set timefmt "%H:%S"
set format x "%H"
set style fill solid 0.6 border -1
set boxwidth 0.3 relative
set xrange["00:00":"23:30"]
set style data boxes plot 'dataset.txt' using 1:2, \ '' using (timecolumn(1)+60*20):($2*0.5), \ '' using (timecolumn(1)+60*40):($2*0.7)

• Animations in Gnuplot can be built using “do for []{…}”;
• Set a circle in the centre: set object circle at …;

#example_1
plot 'dataset.txt' every I:J:K:L:M:N 
plot 'dataset.txt' every 2		# Plot every 2 lines
plot 'dataset.txt' every ::3	        # Plot starting from the 3rd line
plot 'dataset.txt' every ::3::15	# Plot lines 3-15
 
#example_2
do for [t=0:50] {
  outfile = sprintf('animation/bessel%03.0f.png',t)
  set output outfile
  splot u*sin(v),u*cos(v),bessel(u,t/50.0) w pm3d ls 1
  pause 0.02
}

There are two different ways to draw heatmaps with gnuplot:

• Plotting 'with image': This is the best option if no interpolation is required (like it can be done with pm3d) and the X-value and Y-values are evenly distributed (otherwise it does not work).
• Plotting with 'pm3d' and 'splot': Pm3d is a splot style for drawing palette-mapped 3d and 4d data as color/gray maps and surfaces. It uses an algorithm that allows plotting gridded as well as non-gridded data without preprocessing. This is by far the most flexible and advanced plotting style. But it draws every 'pixel' as a coloured polygon, which can also result in huge output files.

Palette is a color storage for use by pm3d, filled color contours or polygons, color histograms, color gradient background.

set palette (i.e. without options): sets up the default values
set palette gray switches to a gray only palette
set palette rgbformulae, set palette defined, set palette file and set palette functionsswitch to a color mapping.
set palette color is an easy way to switch back from the gray palette to the last color mapping.

Interpolate: The option interpolate m,n will interpolate between grid points to generate a finer mesh. For data files, this smooths the color surface and enhances the contrast of spikes in the surface.

How can we include the graphics produced by Gnuplot into a TEX document?

# install texlive
apt-get install texlive 
 
# create 'text.gp' and add
set terminal latex
set out 'plot.tex'
plot [-5:5] [-1.5:1.5] sin(x+pi) title "$\\sin(x+\\pi)$"
set out
 
# run it
gnuplot test.gp
 
# text editor: create example.tex and put some content in it
\documentclass{article}
\begin{document}
\input{plot.tex}
\end{document}
 
# run latex on it to produce some output
# ..don't worry about most of this output -- the important part is the Output written on example.dvi line, which says that it was successful.	
latex example.tex                                   
 
# now you need to view the output file with xdvi
# this will pop up a window with the beautifully formatted output in it. Hit `q' to quit this, or you can leave it open and it will automatically update when the example.dvi file is modified (so whenever you run latex to update the output).
xdvi ex1.dvi &                                     
 
# to produce a PDF of this you simply run pdflatex instead of latex
# ..and you'll have an example.pdf file created instead of the example.dvi file.
pdflatex example.tex