Gnuplot is a useful tool for plotting data, and is available on Ugrad. Start it up by typing "gnuplot". It might be more convenient to do this in a new window, which you can start using "xterm &".
Note: the files used in this tutorial are available in ~afrith/phys2020, so you can get them using "cp ~afrith/phys2020/*.* ."
Gnuplot can plot mathematical functions, which you can write in the same way you would write expressions in C.
Example:
gnuplot>plot sin(x) + sin(x/2)
Gnuplot can plot data in text files, using the plot and splot comands.. Data should be in columns, and data with more than one column should be delimited by either tabs or spaces, not commas.
Example:
gnuplot>plot "1d.dat"
view output
gnuplot>plot "2d.dat"
view output
will plot the data in the file quoted. Two columns of data will be interpreted as x and y axis values, one column of data will be interpreted as y axis values, with the line number of each y value being used as the corresponding x value.
You can also override these defaults and choose which columns to plot.
Example:
gnuplot>plot "3d.dat" using 1:2, "3d.dat" using 1:3
view output
will plot the first column as x values and the third column as y values
Gnuplot can also plot on the z axis using splot.
Example:
gnuplot>splot "3d.dat"
view output
Type "help splot" for more information.
Example:
gnuplot>plot "2d.dat" title 'sin(x) + sin(x/2) + sin(x/4)'
gnuplot>plot "2d.dat" title 'sin(x) + sin(x/2) + sin(x/4)' with linespoints
view output
Example:
gnuplot>set xlabel 'x'
gnuplot>replot
gnuplot>set xrange [0:2]
gnuplot>replotview output
Type "help set" for more information on things you can change.
To save typing in the same commands each time you want to plot some data, you can write a series of gnuplot commands in a file, and then use the load command to run those commands. Lines starting with the "#" character are comments.
Example:
gnuplot>load "script"
