# Eigen Command

This command is used to perform the analysis.

```tcl eigen <$solver> $numEigenvalues ```

numEigenvalues

number of eigenvalues required

solver

optional string detailing type of solver: -genBandArpack, -symmBandLapack, -fullGenLapack (default: -genBandArpack)

RETURNS:

a tcl string containg eigenvalues.

NOTES:

  1. The eigenvectors are stored at the nodes and can be printed out using a Node Recorder, the nodeEigenvector command, or the Print command.
  2. The default eigensolver is able to solve only for N-1 eigenvalues, where N is the number of inertial DOFs. When running into this limitation the -fullGenLapack solver can be used instead of the default Arpack solver.
## Theory
$$\left (K - \lambda M \right ) \Phi = 0 $$

## Examples

set eigenvalues [eigen 10];


Code Developed by: fmk