Choosing Colors for Geometric Graphs via Color Space Embeddings

Graph drawing research traditionally focuses on producing geometric embeddings of graphs satisfying various aesthetic constraints. After the geometric embedding is specified, there is an additional step that is often overlooked or ignored: assigning display colors to the graph's vertices. We study the additional aesthetic criterion of assigning distinct colors to vertices of a geometric graph so that the colors assigned to adjacent vertices are as different from one another as possible. We formulate this as a problem involving perceptual metrics in color space and we develop algorithms for solving this problem by embedding the graph in color space. We also present an application of this work to a distributed load-balancing visualization problem.Comment: 12 pages, 4 figures. To appear at 14th Int. Symp. Graph Drawing, 200

Recommendations for Your Data Visualization Bookshelf

Over the years that I’ve been involved in data visualization, I have collected a number of books on the topic. Not every book in my library is great, but a few stand out as particularly useful for businesspeople who wish to become experts in using visualizations to analyze and communicate quantitative data. I have intentionally not included most of the books that focus on the visualization needs of scientists and statisticians. A few books that venture in this direction have been included, however, because they provide a great deal of general content that is extremely worthwhile, such as those by Edward Tufte and William Cleveland. Fundamentals of Graph Design I will begin the list with those books that cover the fundamentals of graph design for the communication of quantitative business information. Even though it will appear self-promoting, I unapologetically recommend my own book, Show Me the Numbers: Designing Tables and Graphs to Enlighten, as the best available resource on the design of graphs (and tables) for communicating quantitative business information. As someone who has been involved in the business intelligence industry for many years, I am intimately aware of the needs of businesspeople who must make sense of quantitativ

Categorical Colormap Optimization with Visualization Case Studies

—Mapping a set of categorical values to different colors is an elementary technique in data visualization. Users of visualization software routinely rely on the default colormaps provided by a system, or colormaps suggested by software such as ColorBrewer. In practice, users often have to select a set of colors in a semantically meaningful way (e.g., based on conventions, color metaphors, and logological associations), and consequently would like to ensure their perceptual differentiation is optimized. In this paper, we present an algorithmic approach for maximizing the perceptual distances among a set of given colors. We address two technical problems in optimization, i.e., (i) the phenomena of local maxima that halt the optimization too soon, and (ii) the arbitrary reassignment of colors that leads to the loss of the original semantic association. We paid particular attention to different types of constraints that users may wish to impose during the optimization process. To demonstrate the effectiveness of this work, we tested this technique in two case studies. To reach out to a wider range of users, we also developed a web application called Colourmap Hospital

SPRWeb: preserving subjective responses to website colour schemes through automatic recolouring

Colours are an important part of user experiences on the Web. Colour schemes influence the aesthetics, first impressions and long-term engagement with websites. However, five percent of people perceive a subset of all colours because they have colour vision deficiency (CVD), resulting in an unequal and less-rich user experience on the Web. Traditionally, people with CVD have been supported by recolouring tools that improve colour differentiability, but do not consider the subjective properties of colour schemes while recolouring. To address this, we developed SPRWeb, a tool that recolours websites to preserve subjective responses and improve colour differentiability - thus enabling users with CVD to have similar online experiences. To develop SPRWeb, we extended existing models of non-CVD subjective responses to CVD, then used this extended model to steer the recolouring process. In a lab study, we found that SPRWeb did significantly better than a standard recolouring tool at preserving the temperature and naturalness of websites, while achieving similar weight and differentiability preservation. We also found that recolouring did not preserve activity, and hypothesize that visual complexity influences activity more than colour. SPRWeb is the first tool to automatically preserve the subjective and perceptual properties of website colour schemes thereby equalizing the colour-based web experience for people with CVD.Engineering and Applied Science

Categorical colormap optimization with visualization case studies

Mapping a set of categorical values to different colors is an elementary technique in data visualization. Users of visualization software routinely rely on the default colormaps provided by a system, or colormaps suggested by software such as ColorBrewer. In practice, users often have to select a set of colors in a semantically meaningful way (e.g., based on conventions, color metaphors, and logological associations), and consequently would like to ensure their perceptual differentiation is optimized. In this paper, we present an algorithmic approach for maximizing the perceptual distances among a set of given colors. We address two technical problems in optimization, i.e., (i) the phenomena of local maxima that halt the optimization too soon, and (ii) the arbitrary reassignment of colors that leads to the loss of the original semantic association. We paid particular attention to different types of constraints that users may wish to impose during the optimization process. To demonstrate the effectiveness of this work, we tested this technique in two case studies. To reach out to a wider range of users, we also developed a web application called Colourmap Hospital

Examining and Exposing the Darknet

This thesis consists of two studies; the first study is “Diving into the Darknet” and the second is “Exposing the Darknet on Mobile Devices”. The Darknet is a network of hidden sites and services which are built based on anonymity. In “Diving into the Darknet”, we applied different data science methods to establish the relationships between the data in the data set. This data set has information related to seller, drug types, and transactions. Additionally, we used Tableau to visualize the data set. For the second study, we took a digital forensics perspective of the Darknet. Orfox and Orbot, a Browser Bundle which is used to access the Darknet through mobile devices, were installed on a Galaxy Note 5 with Android 6.0.1. After the investigation, some theories of past studies were disproved by our method combined with E3: DS, a mobile digital forensics software package by Paraben. We believe that the combination of information from a user’s point of view and a technical perspective of digital forensics would bring the Darknet to light. Through this thesis, we hope that knowledge about the Darknet will be revealed and better understood