ElementMesh::femimq

范例

This message is generated when mesh elements are specified that self-intersect, have a wrong ordering, or have no area:

Wolfram Language code: Needs["NDSolve`FEM`"]

Wolfram Language code: ToElementMesh["Coordinates" -> {{0, 0}, {1, 0}, {0, 1}}, "MeshElements" -> {TriangleElement[{{3, 2, 1}}]}]

To fix this, the correct element ordering needs to be specified:

Wolfram Language code: ToElementMesh["Coordinates" -> {{0, 0}, {1, 0}, {0, 1}}, "MeshElements" -> {TriangleElement[{{1, 2, 3}}]}]

This message may also be generated during interpolation:

Wolfram Language code: data = {{2.62713, 145.509, 1.}, {2.62713, 155.609, 2.}, {4.50713, 154.346, 2.}, {6.38713, 153.084, 2.}};

Wolfram Language code: Interpolation[data, InterpolationOrder -> 1];

The issue is that because of numerical inexactness, a triangle with 0 area has been generated during mesh creation:

Wolfram Language code: m = ToElementMesh[data[[All, 1 ;; 2]]]

Note that three triangles have been generated and one has poor quality:

Wolfram Language code: m["Quality"]

Visualize the generated mesh:

Wolfram Language code: m["Wireframe"]

Slightly perturbing the input data fixes this:

Wolfram Language code:

data2 = data;
data2[[All, 1 ;; 2]] += RandomReal[10 ^ -12 * {-1, 1}, Dimensions[data2[[All, 1 ;; 2]]]];

Wolfram Language code: if = Interpolation[data2, InterpolationOrder -> 1];

Inspect the quality:

Wolfram Language code: if["ElementMesh"]["Quality"]

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