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I have a 3D list in which the first two numbers (nu, W) of each triple give the coordinates and the third number gives the function value at that coordinate. Here is an example:

FF2 = {{1.4, 0.760089, 5.77799}, {1.45, 0.830541, 8.42173}, {1.5, 0.903465, 
  8.65953}, {1.55, 0.978862, 5.2949}, {1.6, 1.05673, 6.46395}, {1.65, 
  1.13707, 5.39853}, {1.7, 1.21988, 7.35322}, {1.75, 1.30517, 
  7.11009}, {1.8, 1.39292, 7.2419}, {1.85, 1.48315, 6.75664}, {1.9, 
  1.57585, 5.78875}, {1.95, 1.67103, 4.13283}, {2., 1.76867, -5.64055}}

The first coordinate runs from 1.4 to 2.0 in steps of 0.05, the second one irregularly from ~0.76 to ~1.76. I now do ListContourPlot[FF2, PlotLegends -> Automatic, FrameLabel -> {W, nu}] and get contourlines well outside the range of the two coordinates: enter image description here

What does this plot actually mean and what does it represent? The list given above essentially just defines a function along a line in the (nu,W) plane. Shouldn't the contourlines just shrink to points on that line? Why does the plot show strength well outside the range of points? I should add that in the full problem I have many of such independent lines in the (W,nu) plane and am interested in ultimately defining a function over that plane.

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    $\begingroup$ ListContourPlot is kind of like a height map on a regular grid. It might be more appropriate to visualize your data as a curve in 3D space as it clearly doesn't deviate much out of a plane Graphics3D[{Point[FF2], Line[FF2]}, BoxRatios -> 1, Axes -> True]. You could also visualize using BubbleChart[FF2] $\endgroup$
    – flinty
    Aug 18, 2020 at 18:56
  • $\begingroup$ @flinty the BubbleChart suggestion was very useful. Thanks. $\endgroup$
    – user3584513
    Aug 19, 2020 at 15:00

1 Answer 1

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Clear["Global`*"]

FF2 = {{1.4, 0.760089, 5.77799}, {1.45, 0.830541, 8.42173}, {1.5, 0.903465, 
    8.65953}, {1.55, 0.978862, 5.2949}, {1.6, 1.05673, 6.46395}, {1.65, 
    1.13707, 5.39853}, {1.7, 1.21988, 7.35322}, {1.75, 1.30517, 
    7.11009}, {1.8, 1.39292, 7.2419}, {1.85, 1.48315, 6.75664}, {1.9, 1.57585,
     5.78875}, {1.95, 1.67103, 4.13283}, {2., 1.76867, -5.64055}};

The plot that you posted does not correspond to the data that you posted.

ListContourPlot[FF2, PlotLegends -> Automatic, FrameLabel -> {W, nu}]

enter image description here

From the documentation: "ListContourPlot linearly interpolates values to give smooth contours." With a very limited number of points the contours will not be smooth.

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