# Groups¶

Groups are lists of matrix names and we use them to categorize matrices in Matrix Depot. The list below shows all the predefined groups in Matrix Depot and we can extend this list by defining new groups. Group names are noted as symbols, e.g. :symmetric.

## Predefined Groups¶

all
All the matrices in the collection.
data
The matrix has been downloaded from UF sparse matrix collection or the Matrix Market collection.
eigen
Part of the eigensystem of the matrix is explicitly known.
graph
An adjacency matrix of a graph.
illcond
The matrix is ill-conditioned for some parameter values.
inverse
The inverse of the matrix is known explicitly.
posdef
The matrix is positive definite for some parameter values.
random
The matrix has random entries.
regprob
The output is a test problem for Regularization Methods.
sparse
The matrix is sparse.
symmetric
The matrix is symmetric for some parameter values.

New groups can be added with the macro @addgroup:

@addgroup myfav = ["lehmer", "cauchy", "hilb"]

@addgroup test_for_paper2 = ["tridiag", "sampling", "wing"]

listgroups()

Groups:
data          eigen         illcond       inverse
posdef        random        regprob       sparse
symmetric     myfav         test_for_paper2

listnames(:myfav)
3-element Array{ASCIIString,1}:
"lehmer"
"cauchy"
"hilb"