![]() Don’t forget to use the up and down arrow keys to recall previous commands. When you’ve changed settings using the “set” commands you can quickly re-draw your graph using “replot” rather than using the complete plot command. Modifying the y-axis has also ensured the key doesn’t clash with the data lines : ![]() In this final example I’ve changed the data to use “lines” and added a”lw” parameter to increase the line width to 2. Here is a final example : plot "mydata.dat" u 1:2 t "Sine" with lines lw 2, "mydata.dat" u 1:3 t "Cosine" with lines lw 2, "mydata.dat" u 1:4 t "Square" with lines lw 2 You can reset the axis auto-scaling with “set autoscale”. In our example we modified the y-axis and this would give us a plot like this : Or modify your plot command : plot "mydata.dat" u 1:2 t "Sine", "mydata.dat" u 1:3 t "Cosine" Most of the time this is fine but you may want to tweak the axis values to make it look a bit nicer. Customising the Axis Scaleīy default the axis will autoscale. You can use a range of colours including black, red, green, blue, magenta, cyan, brown and light red. Just use the “lt” paramenter : plot "mydata.dat" using 1:2 lt rgb "blue", "mydata.dat" using 1:3 lt rgb "violet" It’s easy to change the colour of your data. You can change the style to “lines” or “linespoints” using the “with” keyword : plot "mydata.dat" u 1:2 t "Sin", "mydata.dat" u 1:4 t "Square" with lines You can also change the way the data points are represented on the graph. By default points are used. To change the axis labels you can use the following commands : set xlabel "Minutes (mins)" This can be abbreviated to : plot "mydata.dat" u 1:2 t "Sin", "mydata.dat" u 1:3 t "Cos" To change the data labels you can modify your plot command : plot "mydata.dat" using 1:2 title "Sin", "mydata.dat" using 1:3 title "Cos" To change the plot title you can type the following command : set title "Example Plot" Many of the customisations you can make to your graph are either made by adding parameters to the “plot” command or issuing “set” commands. This tells gnuplot to plot three sets of data using columns 2, 3 and 4. To plot the two other sets you can type : plot "mydata.dat" using 1:2, "mydata.dat" using 1:3, "mydata.dat" using 1:4 This only plots the data from the 2nd column. To plot data you can enter : plot "mydata.dat" You will be presented with a command prompt awaiting your instructions. You can launch gnuplot by either typing “gnuplot” in a terminal window or using the shortcut under XXXXXX. If you haven’t already launch the graphical environment by typing : startx I used three for this tutorial to make the example plots a bit more interesting. If you were plotting temperature you may only have 1 column of data. The first column is just a number sequence. The script will create “mydata.dat” and the contents will look a bit like this : 0 0.00 0.50 -0.60 Run it using : python gnuplot_generate_data.py You can download this script directly to your Pi using : wget ![]() Each line contains a set of data points where each number is separated with a space character.Ĭo = 0.5 * s(math.radians(degrees))ĭata = "\n".format(degrees,si,co,sq) It creates a plain text file called “mydata.dat”. Here is a simple Python script to create some test data. In order to do the example plots I needed some test data. To install gnuplot on the Raspberry Pi use the following command : sudo apt-get install gnuplot-x11 This tutorial just scratches the surface but aims to provide a quick reference for creating graphs from simple datasets. It’s got a lot of options but it only takes five minutes to master the basics. The answer was yes and came in the form of “gnuplot”, a command-line driven graphing utility. Could I do some simple plots without getting frustrated with tons of obscure command line syntax? In this case I decided to try to do it on the Pi given I was already working wthin the LXDE environment. As a Windows user this is a task I would normally perform in Microsoft Excel or LibreOffice Calc. This involved plotting some data and making some adjustments based on the resulting graph. P.S.: A simple on line gnuplot works (eg plot real(sin(x)**besj0(x))), also shell-escape must be enabled.I was recently testing a sensor which needed calibrating. Is it possible to call a file with code or have multiple lines with function declarations? I'm trying to use multiple lines of code to be plotted with gnuplot with \addplot gnuplot, however this doesn't work and no plot output is created. ![]()
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