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[Jan Stránský <question234676@xxxxxxxxxxxxxxxxxxxxx>]

Question #234676 on Yade changed:
https://answers.launchpad.net/yade/+question/234676

Jan Stránský posted a new comment:
Hello Alexander,


> Yes my question was kind of 'useless'. What I am looking for is the
> stress of each particle so I can map it against its position in 3D
> space, to develop a 3d 'stress map' for various loads, ball size and
> contact parameters. So it sounds like exactly what bodyStressTensors()
> returns. But this function returns a tuple of length 1.
>


Normally the function should behave differently.. the function should
return direcltly list of Matrix3. Don't you have some commas around the
command? In such a case, stresses would really be tuple of size 1. Compare

stresses1 = bodyStressTensors(), # comma at the end
stresses2 = bodyStressTensors()  # no comma
print len(stresses1) # should be 1 (the tuple)
print len(stresses2) # should be equal to len(O.bodies)



>
> I have since found my answer, it turns out it is my amateur python
> skills that let me down.


No problem, we all know that beginnings are tough, so in case of any
questions (even the "useless" once), do not hesitate to ask :-)


> The bodyStressTensors() module returns a tuple
> of length 1, but that single entry is a list of the stress tensor for
> each body (walls and facets included).
>
> i.e.
> stress=utils.bodyStressTensors()
> stress=stress[0]
>
> now 'stress' is a list of tensors (Matrix3) for each body.
>

see my comment above


>
> I assume now I can loop through O.bodies and match the list index number
> of 'stress' to body id numbers to map the stress to the bodies position
> in 3D space.
>

yes, now you can iterate over bodies

stresses = bodyStressTensors()
for b in O.bodies:
  stress = stresses[b.id]
  # now do whatever you want with the stress

or you can access directly specific value

stress = stresses[243] # stress of body with id 243

cheers
Jan

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