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Spectral layout drawing of random small-world network. For comparison, the same graph plotted as spring graph drawing. Spectral layout is a class of algorithm for drawing graphs. The layout uses the eigenvectors of a matrix, such as the Laplace matrix of the graph, as Cartesian coordinates of the graph's vertices.
A pair of graphs are said to be cospectral mates if they have the same spectrum, but are non-isomorphic. The smallest pair of cospectral mates is {K 1,4, C 4 ∪ K 1}, comprising the 5-vertex star and the graph union of the 4-vertex cycle and the single-vertex graph [1].
All forms share the same general layout: stars of greater luminosity are toward the top of the diagram, and stars with higher surface temperature are toward the left side of the diagram. The original diagram displayed the spectral type of stars on the horizontal axis and the absolute visual magnitude on the vertical axis.
Graphic representation of a minute fraction of the WWW, demonstrating hyperlinks.. Graph drawing is an area of mathematics and computer science combining methods from geometric graph theory and information visualization to derive two-dimensional depictions of graphs arising from applications such as social network analysis, cartography, linguistics, and bioinformatics.
In the mathematical field of spectral graph theory, a Ramanujan graph is a regular graph whose spectral gap is almost as large as possible (see extremal graph theory).Such graphs are excellent spectral expanders.
The Spectral layout is based on the spectral properties of the graph's adjacency matrix. It uses the eigenvalues and eigenvectors of the adjacency matrix to position nodes in a low-dimensional space. Spectral layout tends to emphasize the global structure of the graph, making it useful for identifying clusters and communities. [15]
Given a simple graph with vertices , …,, its Laplacian matrix is defined element-wise as [1],:= { = , or equivalently by the matrix =, where D is the degree matrix and A is the adjacency matrix of the graph.
The upper half of this diagram shows the frequency spectrum of a modern switching power supply which employs spread spectrum. The lower half is a waterfall plot showing the variation of the frequency spectrum over time during the power supply's heating up period. Spectrogram and 3 styles of waterfall plot of a whistled sequence of 3 notes vs time