yade-users team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

> I would like to have the history of the contact forces between two
> bodies (say to test a contact law with the Mindlin formulation for kn
> and ks) and I would like to know if it is possible to do that with
> python or if I need c++. I see the following command in python (being
> i a specific interaction);
> 
> i.phys.normalForce
> 
> Could you suggest me how to use this command to get the history and
> not just the value at a specific iteration?

Much easier with python. Add this to engines
(https://www.yade-dem.org/sphinx/yade.wrapper.html#yade.wrapper.PeriodicPythonRunner)

PeriodicPythonRunner(command="someFunction()",iterPeriod=...) # see docs

then define someFunction which will be called.

Actually, have a look at scripts/simple-scene-plot.py, it does exactly
that (and more); you add that engine*, then define the function 

def myAddPlotData():
	plot.addData(fn=O.interactions[34,55].phys.normalForce,step=O.iter) # save data you need, their names ('fn' and 'step') are used below

and finally**

plot.plots={'step':('fn',)}  ## define x-y plot step-fn

After you run simulation, you will have the data in graphs (if you call
plot.plot(), which you can also save to png/pdf...), in file (if you
call plot.saveGnuplot('something')) and in memory (as an array in
plot.data['fn']).

HTH, Vaclav

*) The admonition about 'plotDataCollector' label no longer applies; you
don't have to label the engine at all.

**) If you don't define plot.plots, data will still be saved in memory,
but it is needed for plot.plot() and plot.saveGnuplot(...).