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## 7.12Element selection

feutil FindElt supports a number of element selection criteria that are used by many functions. An element selection command is specified by giving a string command (for example 'GroupAll') to be applied on a model (nodes, elements, possibly alternate element set).

Basic commands are :

• [eltind,elt] = feutil('findelt selector',model);
or elt = feutil('selelt selector',model); this command applies the specified element selection command to a model structure. For example,
[eltind,selelt] = feutil('findelt eltname bar1',model) selects the elements in model.Elt which type is bar1.
• [eltind,elt] = feutil('findelt selector',model);
this command applies the specified element selection command to the standard global matrices FEnode, FEelt, FEel0, …For example, [eltind,selelt] = femesh('findelt eltname bar1') selects the elements in FEelt which type is bar1.

Output arguments are eltind the selected elements indices in the element description matrix and selelt the selected elements.

Accepted selectors are

 ConnectedTo i finds elements in a group that contains the nodes i. This calls feutil DivideInGroups and thus only operates on groups of elements of a single type. EGID i finds elements with element group identifier i. Operators accepted. EltId i finds elements with identificators i in FEelt. Operators accepted. EltInd i finds elements with indices i in FEelt. Operators accepted. EltName s finds elements with element name s. EltName flui will select all elements with name starting with flui. EltName ~= flui will select all elements with name not starting with flui. One can select superelements from their name using EltName SE:SEName. Facing > cos x y z finds topologically 2-D elements whose normal projected on the direction from the element CG to x y z has a value superior to cos. Inequality operations are accepted. Group i finds elements in group(s) i. Operators accepted. InNode i finds elements with all nodes in the set i. Nodes numbers in i can be replaced by a string between braces defining a node selection command. For example femesh('find elt withnode {y>-230 & NodeId>1000}'). MatId i finds elements with MatId equal to i. Relational operators are also accepted (MatId =1:3, ...). ProId i finds elements with ProId equal to i. Operators accepted. SelEdge type selects the external edges (lines) of the currently selected elements (any element selected before the SelEdge selector), any further selector is applied on the model resulting from the SelEdge command rather than on the original model. The -KeepAll option skips the internal edge elimination step. Type g retains inter-group edges. m retains inter-material edges. Type p retains inter-property edges. all retains all edges. The MatId for the resulting model identifies the original properties of each side of the edge. SelFace type selects the external faces (surfaces) of the currently selected elements. The face number is stored in the column after EltId to allow set generation. See more details under SelEdge. The -KeepAll option skips the internal face elimination step. WithNode i finds elements with at least one node in the set i. i can be a list of node numbers. Replacements for i are accepted as above. SetName s finds elements in element set named s (see set stack entries). `SetName "name:con IdList"` can be used to select a subset connected to nodes in the IdList (assuming the .NodeCon field is defined). WithoutNode i finds elements without any of the nodes in the set i. i can be a list of node numbers. Replacements for i are accepted as above.

Different selectors can be chained using the logical operations & (finds elements that verify both conditions), | (finds elements that verify one or both conditions). femesh('FindEltGroup 1:3 & with node 1 8') for example. Condition combinations are always evaluated from left to right (parentheses are not accepted).

Command option epsl value can be used to give an evaluation tolerance for equality logical operators.

Numeric values to the command can be given as additional femesh arguments. Thus the command above could also have been written femesh('findelt group & withnode',1:3,[1 8]).