Using gnuplot to plot probe data
 

Hello everyone.


I started using gnuplot because it is a convenient tool to plot data. Basically, you just have to type a line or two in a terminal to have your data plotted.
Yet I don't understand the syntax, I found a way to plot my residuals using an openfoam command which extracts the data in my log file and puts it in a single column text file. This way I can tell gnuplot to plot it correctly using simple commands.
This is what I do :


foamLog -n "name of my log file"
gnuplot
plot './Uz_0'


It works well for single column data files created by foamLog. Now my problem is that I want to do the same with probes. Often, my probe files are two columns files, time/iteration versus quantity of interest. But for the velocity, the file is much more complicated with "(" and ")" and four columns.


Is there a simple way to tell gnuplot how to plot a two column file ? Is there an openFoam utility that can convert the velocity probe file into something more manageable like several one column files, as foamLog does for the logfile ?


Thank you all for any input.

Hi,

Not an OpenFOAM utility, but sed would work for this:

Or if you just want to keep the file, you can do replacement inside the file itself as:

And than plot on the U_noBrackets or new U file.

Regards,
Tom

Thank you for your answer tomf, it was helpful.


For those who will read this, here is the gnuplot syntax to plot a file with multiple columns : https://stackoverflow.com/questions/...-all-on-y-axis


Another thing : I realised that gnuplot can actually handle parenthesis. You don't need to remove them before trying to plot. Looks like it just ignores them, which is practical.

To all the FOAMers...

This is a small attempt to save ur time:).....The following script can be be used to monitor as well as export the probes of pressure, velocity and temperature. The script is written for 3 probe points....you might need to edit it accordingly as per the number of probes and fields that u r observing