and therefore we will illustrate it by looking at a few examples. Sometimes the visual representation of a matrix is directly available, for instance if the matrix is based on a triangulated mesh, such as the following . In other cases, the visual representation can be generated from the problem that the matrix represents, see . If no such information is available at all, we generate the visual representation ourselves, as discussed in .

\[exa:pothen\] The `pothen` collection of matrices, available from [@Davis2010], consists of NASA structural engineering matrices collected by A. Pothen. We will take a closer look at the square pattern[^3] matrices from this collection, which have a natural visual representation. Each row/column of these matrices corresponds to a vertex (the coordinates of which are supplied in a separate file) and each nonzero to an edge between the vertices corresponding to the row and column to which the nonzero belongs. We can take a look at the matrices and their corresponding visual representation by plotting these vertices, as is done in . These vertices give a visual representation of the symmetric hypergraph representation of the sparse matrix.

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   ![From left to right: the matrices `sphere3`, `pwt`, 