Can anyone help, why ListVectorPlot and ListStreamPlot show vectors and streamlines lying outside the allowed domain? Here is my Mathematica code:

pp = Table[{r Cos[ϕ], r Sin[ϕ]}, {r, 0, 10, 
    0.5}, {ϕ, -π/6, π/6, 0.1}];
vv = Table[{{r Cos[ϕ], r Sin[ϕ]}, {1, 0}}, {r, 0, 10, 
    0.5}, {ϕ, -π/6, π/6, 0.1}];
GraphicsRow[{ListPlot[pp], ListVectorPlot[vv], ListStreamPlot[vv]}]

And I get the plots:

enter image description here

Why do the vectors in the second and third cases fill the whole square instead of the section of a circle?

  • $\begingroup$ Because ListVectorPlot performs interpolation. $\endgroup$ – Feyre Oct 28 '16 at 21:50


region = Function[{x, y, vx, vy, n}, 
   Sqrt[x^2 + y^2] < 10 && x != 0 && -π/6 < ArcTan[y/x] < π/6];

  ListVectorPlot[vv, RegionFunction -> region], 
  ListStreamPlot[vv, RegionFunction -> region]}]

enter image description here

  • $\begingroup$ Thank you. It works, but I still do not understand, why Mathematica plotted vectors beyond the domain, and why one should to impose this domain again on the plot. $\endgroup$ – Tomala Oct 28 '16 at 22:22

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