# [Gmsh] logarithmic scale and vector arrows

**Kubicek Bernhard**
Bernhard.Kubicek at arsenal.ac.at

*Wed Jan 17 20:37:56 CET 2007*

Hello Milan,
I just found a way of displaying a vector field with arraows that
logarithmicly scaled in length.
Right-click the field in the gmsh-interface->Plugins->Extract.
Into the expression0-3 fields put this lines respectively:
v0/Sqrt(v0^2+v1^2+v2^2)*Log(Sqrt(v0^2+v1^2+v2^2))
v1/Sqrt(v0^2+v1^2+v2^2)*Log(Sqrt(v0^2+v1^2+v2^2))
v2/Sqrt(v0^2+v1^2+v2^2)*Log(Sqrt(v0^2+v1^2+v2^2))
Expression3-8 need to be completely empty. Also, one might want to use
Log10 instead of Log.
Check that iView contains the numer of the view, from which you want to
display the log-arrows.
Finally click Run, and (hopefully) enjoy.
Of course, one might prefer if there are no zero-length vectors in the
orignal field.
nice greetings,
Bernhard