76 research outputs found
A Coloring Algorithm for Disambiguating Graph and Map Drawings
Drawings of non-planar graphs always result in edge crossings. When there are
many edges crossing at small angles, it is often difficult to follow these
edges, because of the multiple visual paths resulted from the crossings that
slow down eye movements. In this paper we propose an algorithm that
disambiguates the edges with automatic selection of distinctive colors. Our
proposed algorithm computes a near optimal color assignment of a dual collision
graph, using a novel branch-and-bound procedure applied to a space
decomposition of the color gamut. We give examples demonstrating the
effectiveness of this approach in clarifying drawings of real world graphs and
maps
Galactic vs. Extragalactic Origin of the Peculiar Transient SCP 06F6
We study four scenarios for the SCP 06F6 transient event that was announced
recently. Some of these were previously briefly discussed as plausible models
for SCP 06F6, in particular with the claimed detection of a z=0.143
cosmological redshift of a Swan spectrum of a carbon rich envelope. We adopt
this value of z for extragalactic scenarios. We cannot rule out any of these
models, but can rank them from most to least preferred. Our favorite model is a
tidal disruption of a CO white dwarf (WD) by an intermediate-mass black hole
(IMBH). To account for the properties of the SCP 06F6 event, we have to assume
the presence of a strong disk wind that was not included in previous numerical
simulations. If the IMBH is the central BH of a galaxy, this explains the non
detection of a bright galaxy in the direction of SCP 06F6. Our second favorite
scenario is a type Ia-like SN that exploded inside the dense wind of a carbon
star. The carbon star is the donor star of the exploded WD. Our third favorite
model is a Galactic source of an asteroid that collided with a WD. Such a
scenario was discussed in the past as the source of dusty disks around WDs, but
no predictions exist regarding the appearance of such an event. Our least
favorite model is of a core collapse SN. The only way we can account for the
properties of SCP 06F6 with a core collapse SN is if we assume the occurrence
of a rare type of binary interaction.Comment: Accepted by New Astronom
Stress-Minimizing Orthogonal Layout of Data Flow Diagrams with Ports
We present a fundamentally different approach to orthogonal layout of data
flow diagrams with ports. This is based on extending constrained stress
majorization to cater for ports and flow layout. Because we are minimizing
stress we are able to better display global structure, as measured by several
criteria such as stress, edge-length variance, and aspect ratio. Compared to
the layered approach, our layouts tend to exhibit symmetries, and eliminate
inter-layer whitespace, making the diagrams more compact
Evolutionary Meta Layout of Graphs
A graph drawing library is like a toolbox, allowing experts to select and configure a specialized algorithm in order to meet the requirements of their diagram visualization application. However, without expert knowledge of the algorithms the potential of such a toolbox cannot be fully exploited. This gives rise to the question whether the process of selecting and configuring layout algorithms can be automated such that good layouts are produced. In this paper we call this kind of automation "meta layout." We propose a genetic representation that can be used in meta heuristics for meta layout and contribute new metrics for the evaluation of graph drawings. Furthermore, we examine the use of an evolutionary algorithm to search for optimal solutions and evaluate this approach both with automatic experiments and a user study. The results confirm that our methods can actually help users to find good layout configurations
Incremental Grid-like Layout Using Soft and Hard Constraints
We explore various techniques to incorporate grid-like layout conventions
into a force-directed, constraint-based graph layout framework. In doing so we
are able to provide high-quality layout---with predominantly axis-aligned
edges---that is more flexible than previous grid-like layout methods and which
can capture layout conventions in notations such as SBGN (Systems Biology
Graphical Notation). Furthermore, the layout is easily able to respect
user-defined constraints and adapt to interaction in online systems and diagram
editors such as Dunnart.Comment: Accepted to Graph Drawing 201
Visualization of Frequent Itemsets with Nested Circular Layout and Bundling Algorithm
International audienceFrequent itemset mining is one of the major data mining issues. Once generated by algorithms, the itemsets can be automatically processed, for instance to extract association rules. They can also be explored with visual tools, in order to analyze the emerging patterns. Graphical itemsets representation is a convenient way to obtain an overview of the global interaction structure. However, when the complexity of the database increases, the network may become unreadable. In this paper, we propose to display itemsets on concentric circles, each one being organized to lower the intricacy of the graph through an optimization process. Thanks to a graph bundling algorithm, we finally obtain a compact representation of a large set of itemsets that is easier to exploit. Colors accumulation and interaction operators facilitate the exploration of the new bundle graph and to illustrate how much an itemset is supported by the data
Lombardi Drawings of Graphs
We introduce the notion of Lombardi graph drawings, named after the American
abstract artist Mark Lombardi. In these drawings, edges are represented as
circular arcs rather than as line segments or polylines, and the vertices have
perfect angular resolution: the edges are equally spaced around each vertex. We
describe algorithms for finding Lombardi drawings of regular graphs, graphs of
bounded degeneracy, and certain families of planar graphs.Comment: Expanded version of paper appearing in the 18th International
Symposium on Graph Drawing (GD 2010). 13 pages, 7 figure
Graph Layouts by t‐SNE
We propose a new graph layout method based on a modification of the t-distributed Stochastic Neighbor Embedding (t-SNE) dimensionality reduction technique. Although t-SNE is one of the best techniques for visualizing high-dimensional data as 2D scatterplots, t-SNE has not been used in the context of classical graph layout. We propose a new graph layout method, tsNET, based on representing a graph with a distance matrix, which together with a modified t-SNE cost function results in desirable layouts. We evaluate our method by a formal comparison with state-of-the-art methods, both visually and via established quality metrics on a comprehensive benchmark, containing real-world and synthetic graphs. As evidenced by the quality metrics and visual inspection, tsNET produces excellent layouts
Improved Approximation Algorithms for Box Contact Representations ⋆
Abstract. We study the following geometric representation problem: Given a graph whose vertices correspond to axis-aligned rectangles with fixed dimensions, arrange the rectangles without overlaps in the plane such that two rectangles touch if the graph contains an edge between them. This problem is called CONTACT REPRESENTATION OF WORD NETWORKS (CROWN) since it formalizes the geometric problem behind drawing word clouds in which semantically related words are close to each other. CROWN is known to be NP-hard, and there are approximation algorithms for certain graph classes for the optimization version, MAX-CROWN, in which realizing each desired adjacency yields a certain profit. We present the first O(1)-approximation algorithm for the general case, when the input is a complete weighted graph, and for the bipartite case. Since the subgraph of realized adjacencies is necessarily planar, we also consider several planar graph classes (namely stars, trees, outerplanar, and planar graphs), improving upon the known results. For some graph classes, we also describe improvements in the unweighted case, where each adjacency yields the same profit. Finally, we show that the problem is APX-hard on bipartite graphs of bounded maximum degree.
- …