# gf_mesh_fem_get¶

**Synopsis**

```
n = gf_mesh_fem_get(mesh_fem MF, 'nbdof')
n = gf_mesh_fem_get(mesh_fem MF, 'nb basic dof')
DOF = gf_mesh_fem_get(mesh_fem MF, 'dof from cv',mat CVids)
DOF = gf_mesh_fem_get(mesh_fem MF, 'basic dof from cv',mat CVids)
{DOFs, IDx} = gf_mesh_fem_get(mesh_fem MF, 'dof from cvid'[, mat CVids])
{DOFs, IDx} = gf_mesh_fem_get(mesh_fem MF, 'basic dof from cvid'[, mat CVids])
gf_mesh_fem_get(mesh_fem MF, 'non conformal dof'[, mat CVids])
gf_mesh_fem_get(mesh_fem MF, 'non conformal basic dof'[, mat CVids])
gf_mesh_fem_get(mesh_fem MF, 'qdim')
{FEMs, CV2F} = gf_mesh_fem_get(mesh_fem MF, 'fem'[, mat CVids])
CVs = gf_mesh_fem_get(mesh_fem MF, 'convex_index')
bB = gf_mesh_fem_get(mesh_fem MF, 'is_lagrangian'[, mat CVids])
bB = gf_mesh_fem_get(mesh_fem MF, 'is_equivalent'[, mat CVids])
bB = gf_mesh_fem_get(mesh_fem MF, 'is_polynomial'[, mat CVids])
bB = gf_mesh_fem_get(mesh_fem MF, 'is_reduced')
bB = gf_mesh_fem_get(mesh_fem MF, 'reduction matrix')
bB = gf_mesh_fem_get(mesh_fem MF, 'extension matrix')
Vr = gf_mesh_fem_get(mesh_fem MF, 'reduce vector', vec V)
Ve = gf_mesh_fem_get(mesh_fem MF, 'extend vector', vec V)
DOFs = gf_mesh_fem_get(mesh_fem MF, 'basic dof on region',mat Rs)
DOFs = gf_mesh_fem_get(mesh_fem MF, 'dof on region',mat Rs)
DOFpts = gf_mesh_fem_get(mesh_fem MF, 'dof nodes'[, mat DOFids])
DOFpts = gf_mesh_fem_get(mesh_fem MF, 'basic dof nodes'[, mat DOFids])
DOFP = gf_mesh_fem_get(mesh_fem MF, 'dof partition')
gf_mesh_fem_get(mesh_fem MF, 'save',string filename[, string opt])
gf_mesh_fem_get(mesh_fem MF, 'char'[, string opt])
gf_mesh_fem_get(mesh_fem MF, 'display')
m = gf_mesh_fem_get(mesh_fem MF, 'linked mesh')
m = gf_mesh_fem_get(mesh_fem MF, 'mesh')
gf_mesh_fem_get(mesh_fem MF, 'export to vtk',string filename, ... ['ascii'], U, 'name'...)
gf_mesh_fem_get(mesh_fem MF, 'export to dx',string filename, ...['as', string mesh_name][,'edges']['serie',string serie_name][,'ascii'][,'append'], U, 'name'...)
gf_mesh_fem_get(mesh_fem MF, 'export to pos',string filename[, string name][[,mesh_fem mf1], mat U1, string nameU1[[,mesh_fem mf2], mat U2, string nameU2,...]])
gf_mesh_fem_get(mesh_fem MF, 'dof_from_im',mesh_im mim[, int p])
U = gf_mesh_fem_get(mesh_fem MF, 'interpolate_convex_data',mat Ucv)
z = gf_mesh_fem_get(mesh_fem MF, 'memsize')
gf_mesh_fem_get(mesh_fem MF, 'has_linked_mesh_levelset')
gf_mesh_fem_get(mesh_fem MF, 'linked_mesh_levelset')
U = gf_mesh_fem_get(mesh_fem MF, 'eval', expr [, DOFLST])
```

**Description :**

General function for inquiry about mesh_fem objects.

**Command list :**

`n = gf_mesh_fem_get(mesh_fem MF, 'nbdof')`

Return the number of degrees of freedom (dof) of the mesh_fem.

`n = gf_mesh_fem_get(mesh_fem MF, 'nb basic dof')`

Return the number of basic degrees of freedom (dof) of the mesh_fem.

`DOF = gf_mesh_fem_get(mesh_fem MF, 'dof from cv',mat CVids)`

Deprecated function. Use gf_mesh_fem_get(mesh_fem MF, ‘basic dof from cv’) instead.

`DOF = gf_mesh_fem_get(mesh_fem MF, 'basic dof from cv',mat CVids)`

Return the dof of the convexes listed in CVids.

WARNING: the Degree of Freedom might be returned in ANY order, do not use this function in your assembly routines. Use ‘basic dof from cvid’ instead, if you want to be able to map a convex number with its associated degrees of freedom.

One can also get the list of basic dof on a set on convex faces, by indicating on the second row of CVids the faces numbers (with respect to the convex number on the first row).

`{DOFs, IDx} = gf_mesh_fem_get(mesh_fem MF, 'dof from cvid'[, mat CVids])`

Deprecated function. Use gf_mesh_fem_get(mesh_fem MF, ‘basic dof from cvid’) instead.

`{DOFs, IDx} = gf_mesh_fem_get(mesh_fem MF, 'basic dof from cvid'[, mat CVids])`

Return the degrees of freedom attached to each convex of the mesh.

If CVids is omitted, all the convexes will be considered (equivalent to CVids = 1 … gf_mesh_get(mesh M, ‘max cvid’)).

IDx is a row vector, length(IDx) = length(CVids)+1. DOFs is a row vector containing the concatenated list of dof of each convex in CVids. Each entry of IDx is the position of the corresponding convex point list in DOFs. Hence, for example, the list of points of the second convex is DOFs(IDx(2):IDx(3)-1).

If CVids contains convex #id which do not exist in the mesh, their point list will be empty.

`gf_mesh_fem_get(mesh_fem MF, 'non conformal dof'[, mat CVids])`

Deprecated function. Use gf_mesh_fem_get(mesh_fem MF, ‘non conformal basic dof’) instead.

`gf_mesh_fem_get(mesh_fem MF, 'non conformal basic dof'[, mat CVids])`

Return partially linked degrees of freedom.

Return the basic dof located on the border of a convex and which belong to only one convex, except the ones which are located on the border of the mesh. For example, if the convex ‘a’ and ‘b’ share a common face, ‘a’ has a P1 FEM, and ‘b’ has a P2 FEM, then the basic dof on the middle of the face will be returned by this function (this can be useful when searching the interfaces between classical FEM and hierarchical FEM).

`gf_mesh_fem_get(mesh_fem MF, 'qdim')`

Return the dimension Q of the field interpolated by the mesh_fem.

By default, Q=1 (scalar field). This has an impact on the dof numbering.

`{FEMs, CV2F} = gf_mesh_fem_get(mesh_fem MF, 'fem'[, mat CVids])`

Return a list of FEM used by the mesh_fem.

FEMs is an array of all fem objects found in the convexes given in CVids. If CV2F was supplied as an output argument, it contains, for each convex listed in CVids, the index of its correspounding FEM in FEMs.

Convexes which are not part of the mesh, or convexes which do not have any FEM have their correspounding entry in CV2F set to -1.

Example:

cvid=gf_mesh_get(mf,'cvid'); [f,c2f]=gf_mesh_fem_get(mf, 'fem'); for i=1:size(f), sf{i}=gf_fem_get('char',f(i)); end; for i=1:size(c2f), disp(sprintf('the fem of convex %d is %s',... cvid(i),sf{i})); end;

`CVs = gf_mesh_fem_get(mesh_fem MF, 'convex_index')`

Return the list of convexes who have an FEM.

`bB = gf_mesh_fem_get(mesh_fem MF, 'is_lagrangian'[, mat CVids])`

Test if the mesh_fem is Lagrangian.

Lagrangian means that each base function Phi[i] is such that Phi[i](P[j]) = delta(i,j), where P[j] is the dof location of the jth base function, and delta(i,j) = 1 if i==j, else 0.

If CVids is omitted, it returns 1 if all convexes in the mesh are Lagrangian. If CVids is used, it returns the convex indices (with respect to CVids) which are Lagrangian.

`bB = gf_mesh_fem_get(mesh_fem MF, 'is_equivalent'[, mat CVids])`

Test if the mesh_fem is equivalent.

See gf_mesh_fem_get(mesh_fem MF, ‘is_lagrangian’)

`bB = gf_mesh_fem_get(mesh_fem MF, 'is_polynomial'[, mat CVids])`

Test if all base functions are polynomials.

See gf_mesh_fem_get(mesh_fem MF, ‘is_lagrangian’)

`bB = gf_mesh_fem_get(mesh_fem MF, 'is_reduced')`

Return 1 if the optional reduction matrix is applied to the dofs.

`bB = gf_mesh_fem_get(mesh_fem MF, 'reduction matrix')`

Return the optional reduction matrix.

`bB = gf_mesh_fem_get(mesh_fem MF, 'extension matrix')`

Return the optional extension matrix.

`Vr = gf_mesh_fem_get(mesh_fem MF, 'reduce vector', vec V)`

Multiply the provided vector V with the extension matrix of the mesh_fem.

`Ve = gf_mesh_fem_get(mesh_fem MF, 'extend vector', vec V)`

Multiply the provided vector V with the reduction matrix of the mesh_fem.

`DOFs = gf_mesh_fem_get(mesh_fem MF, 'basic dof on region',mat Rs)`

Return the list of basic dof (before the optional reduction) lying on one of the mesh regions listed in Rs.

More precisely, this function returns the basic dof whose support is non-null on one of regions whose #ids are listed in Rs (note that for boundary regions, some dof nodes may not lie exactly on the boundary, for example the dof of Pk(n,0) lies on the center of the convex, but the base function in not null on the convex border).

`DOFs = gf_mesh_fem_get(mesh_fem MF, 'dof on region',mat Rs)`

Return the list of dof (after the optional reduction) lying on one of the mesh regions listed in Rs.

More precisely, this function returns the basic dof whose support is non-null on one of regions whose #ids are listed in Rs (note that for boundary regions, some dof nodes may not lie exactly on the boundary, for example the dof of Pk(n,0) lies on the center of the convex, but the base function in not null on the convex border).

For a reduced mesh_fem a dof is lying on a region if its potential corresponding shape function is nonzero on this region. The extension matrix is used to make the correspondence between basic and reduced dofs.

`DOFpts = gf_mesh_fem_get(mesh_fem MF, 'dof nodes'[, mat DOFids])`

Deprecated function. Use gf_mesh_fem_get(mesh_fem MF, ‘basic dof nodes’) instead.

`DOFpts = gf_mesh_fem_get(mesh_fem MF, 'basic dof nodes'[, mat DOFids])`

Get location of basic degrees of freedom.

Return the list of interpolation points for the specified dof #IDs in DOFids (if DOFids is omitted, all basic dof are considered).

`DOFP = gf_mesh_fem_get(mesh_fem MF, 'dof partition')`

Get the ‘dof_partition’ array.

Return the array which associates an integer (the partition number) to each convex of the mesh_fem. By default, it is an all-zero array. The degrees of freedom of each convex of the mesh_fem are connected only to the dof of neighboring convexes which have the same partition number, hence it is possible to create partially discontinuous mesh_fem very easily.

`gf_mesh_fem_get(mesh_fem MF, 'save',string filename[, string opt])`

Save a mesh_fem in a text file (and optionally its linked mesh object if opt is the string ‘with_mesh’).

`gf_mesh_fem_get(mesh_fem MF, 'char'[, string opt])`

Output a string description of the mesh_fem.

By default, it does not include the description of the linked mesh object, except if opt is ‘with_mesh’.

`gf_mesh_fem_get(mesh_fem MF, 'display')`

displays a short summary for a mesh_fem object.

`m = gf_mesh_fem_get(mesh_fem MF, 'linked mesh')`

Return a reference to the mesh object linked to mf.

`m = gf_mesh_fem_get(mesh_fem MF, 'mesh')`

Return a reference to the mesh object linked to mf. (identical to gf_mesh_get(mesh M, ‘linked mesh’))

`gf_mesh_fem_get(mesh_fem MF, 'export to vtk',string filename, ... ['ascii'], U, 'name'...)`

Export a mesh_fem and some fields to a vtk file.

The FEM and geometric transformations will be mapped to order 1 or 2 isoparametric Pk (or Qk) FEMs (as VTK does not handle higher order elements). If you need to represent high-order FEMs or high-order geometric transformations, you should consider gf_slice_get(slice S, ‘export to vtk’).

`gf_mesh_fem_get(mesh_fem MF, 'export to dx',string filename, ...['as', string mesh_name][,'edges']['serie',string serie_name][,'ascii'][,'append'], U, 'name'...)`

Export a mesh_fem and some fields to an OpenDX file.

This function will fail if the mesh_fem mixes different convex types (i.e. quads and triangles), or if OpenDX does not handle a specific element type (i.e. prism connections are not known by OpenDX).

The FEM will be mapped to order 1 Pk (or Qk) FEMs. If you need to represent high-order FEMs or high-order geometric transformations, you should consider gf_slice_get(slice S, ‘export to dx’).

`gf_mesh_fem_get(mesh_fem MF, 'export to pos',string filename[, string name][[,mesh_fem mf1], mat U1, string nameU1[[,mesh_fem mf2], mat U2, string nameU2,...]])`

Export a mesh_fem and some fields to a pos file.

The FEM and geometric transformations will be mapped to order 1 isoparametric Pk (or Qk) FEMs (as GMSH does not handle higher order elements).

`gf_mesh_fem_get(mesh_fem MF, 'dof_from_im',mesh_im mim[, int p])`

Return a selection of dof who contribute significantly to the mass-matrix that would be computed with mf and the integration method mim.

p represents the dimension on what the integration method operates (default p = mesh dimension).

IMPORTANT: you still have to set a valid integration method on the convexes which are not crosses by the levelset!

`U = gf_mesh_fem_get(mesh_fem MF, 'interpolate_convex_data',mat Ucv)`

Interpolate data given on each convex of the mesh to the mesh_fem dof. The mesh_fem has to be lagrangian, and should be discontinuous (typically an FEM_PK(N,0) or FEM_QK(N,0) should be used).

The last dimension of the input vector Ucv should have gf_mesh_get(mesh M, ‘max cvid’) elements.

Example of use: gf_mesh_fem_get(mesh_fem MF, ‘interpolate_convex_data’, gf_mesh_get(mesh M, ‘quality’))

`z = gf_mesh_fem_get(mesh_fem MF, 'memsize')`

Return the amount of memory (in bytes) used by the mesh_fem object.

The result does not take into account the linked mesh object.

`gf_mesh_fem_get(mesh_fem MF, 'has_linked_mesh_levelset')`

Is a mesh_fem_level_set or not.

`gf_mesh_fem_get(mesh_fem MF, 'linked_mesh_levelset')`

if it is a mesh_fem_level_set gives the linked mesh_level_set.

`U = gf_mesh_fem_get(mesh_fem MF, 'eval', expr [, DOFLST])`

Call gf_mesh_fem_get_eval. This function interpolates an expression on a lagrangian mesh_fem (for all dof except if DOFLST is specified). The expression can be a numeric constant, or a cell array containing numeric constants, string expressions or function handles. For example:

U1=gf_mesh_fem_get(mf,'eval',1) U2=gf_mesh_fem_get(mf,'eval',[1;0]) % output has two rows U3=gf_mesh_fem_get(mf,'eval',[1 0]) % output has one row, only valid if qdim(mf)==2 U4=gf_mesh_fem_get(mf,'eval',{'x';'y.*z';4;@myfunctionofxyz})