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b3m2a1

01:34

Sigh. Can anyone help me with getting Filling to work properly. I'm currently trying to fill part of a line plot to the Y-axis, so I constructed three curves along this range and tried to fill between pairs. Here's my attempt:

ListLinePlot[
 {{{0, 17.5`}, {18, 17.5`}, {55, 18.5`}, {59, 19.5`}}, {{0,
    19.5`}, {59, 19.5`}}, {{59, 19.5`}, {50, 20.5`}, {21, 21.5`}, {10,
     22.5`}, {4, 23.5`}, {0, 23.5`}}},
 Filling -> {1 -> {2}, 3 -> {2}}
 ]

Unfortunately I see this...

It's ignoring the 3->{2} completely and I can't understand why.

C. E.

02:02

@b3m2a1 It will work as you expect if you sort the third data series by the x value: SortBy[{{59, 19.5}, {50, 20.5}, {21, 21.5}, {10, 22.5}, {4, 23.5}, {0, 23.5}}, First]

b3m2a1

02:13

@C.E. Ah oh course... I should have known it'd be something unintuitive like that.

2 hours later…

idonutunderstand

04:21

Graphics3D[KnotData["Trefoil", "ImageData"], Axes -> True] is there a good way to center this trefoil around (0,0,0)?

Or, what I really want is for it to not wobble when it rotates: gr = KnotData["Trefoil", "ImageData"] ;
rotAbout = {0, 0, 1};
Manipulate[rot = RotationMatrix[a, rotAbout];
Graphics3D[{Specularity[GrayLevel[1], 100],
GeometricTransformation[gr, rot]}, Boxed -> False,
Lighting -> "Neutral", SphericalRegion -> True,
Background -> Black], {a, 0, 2 Pi, .3}]

2 hours later…

b3m2a1

06:21

@idonutunderstand try this:

With[{g = KnotData["Trefoil", "ImageData"]},
 Graphics3D[
  ReplacePart[g, 1 -> Translate[g[[1]], -Mean@g[[1, 1]]]],
  Boxed -> False,
  Axes -> True,
  AxesOrigin -> {0, 0, 0}
  ]
 ]

Just to show it at work:

With[{g = KnotData["Trefoil", "ImageData"]},
 With[{m = Mean@g[[1, 1]]},
  With[
   {
    gins =
     ReplacePart[g,
      1 ->
       GeometricTransformation[
        Translate[g[[1]], -m],
        RotationTransform[\[Theta], {0, 0, 1}]
        ]
      ]
    },
   Animate[
    Graphics3D[
     gins,
     Boxed -> False,
     Axes -> True,
     AxesOrigin -> {0, 0, 0},
     PlotRange -> {5, 5, 5}
     ],
    {\[Theta], 0, 2 \[Pi]}
    ]
   ]
  ]
 ]

7 hours later…

halirutan

13:50

@idonutunderstand I'm not entirely sure why they would have such a weird shift in the coordinates when you access "ImageData" of the knot-data. When you use the parametric form directly, it is centered perfectly:

ParametricPlot3D[KnotData["Trefoil", "SpaceCurve"][t], {t, 0, 2 Pi}]

If you want to learn something, then use the space-curve, create a local frame and make the tube yourself.

2 hours later…

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