Algorithms for Visualizing Phylogenetic Networks

We study the problem of visualizing phylogenetic networks, which are extensions of the Tree of Life in biology. We use a space filling visualization method, called DAGmaps, in order to obtain clear visualizations using limited space. In this paper, we restrict our attention to galled trees and galled networks and present linear time algorithms for visualizing them as DAGmaps.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016

Uncertainty in phylogenetic tree estimates

Estimating phylogenetic trees is an important problem in evolutionary biology, environmental policy and medicine. Although trees are estimated, their uncertainties are discarded by mathematicians working in tree space. Here we explicitly model the multivariate uncertainty of tree estimates. We consider both the cases where uncertainty information arises extrinsically (through covariate information) and intrinsically (through the tree estimates themselves). The importance of accounting for tree uncertainty in tree space is demonstrated in two case studies. In the first instance, differences between gene trees are small relative to their uncertainties, while in the second, the differences are relatively large. Our main goal is visualization of tree uncertainty, and we demonstrate advantages of our method with respect to reproducibility, speed and preservation of topological differences compared to visualization based on multidimensional scaling. The proposal highlights that phylogenetic trees are estimated in an extremely high-dimensional space, resulting in uncertainty information that cannot be discarded. Most importantly, it is a method that allows biologists to diagnose whether differences between gene trees are biologically meaningful, or due to uncertainty in estimation.Comment: Final version accepted to Journal of Computational and Graphical Statistic

Exploring Hierarchical Visualization Designs Using Phylogenetic Trees

Ongoing research on information visualization has produced an ever-increasing number of visualization designs. Despite this activity, limited progress has been made in categorizing this large number of information visualizations. This makes understanding their common design features challenging, and obscures the yet unexplored areas of novel designs. With this work, we provide categorization from an evolutionary perspective, leveraging a computational model to represent evolutionary processes, the phylogenetic tree. The result — a phylogenetic tree of a design corpus of hierarchical visualizations — enables better understanding of the various design features of hierarchical information visualizations, and further illuminates the space in which the visualizations lie, through support for interactive clustering and novel design suggestions. We demonstrate these benefits with our software system, where a corpus of two-dimensional hierarchical visualization designs is constructed into a phylogenetic tree. This software system supports visual interactive clustering and suggesting for novel designs; the latter capacity is also demonstrated via collaboration with an artist who sketched new designs using our system

Lifemap: Exploring the Entire Tree of Life

International audienceThe Tree of Life (ToL) is meant to be a unique representation of the evolutionary relationships between all species on earth. Huge efforts are made to assemble such a large tree, helped by the decrease of sequencing costs and improved methods to reconstruct and combine phylogenies, but no tool exists today to explore the ToL in its entirety in a satisfying manner. By combining methods used in modern cartography, such as OpenStreetMap, with a new way of representing tree-like structures, I created Lifemap, a tool allowing the exploration of a complete representation of the ToL (between 800,000 and 2.2 million species depending on the data source) in a zoomable interface. A server version of Lifemap also allows users to visualize their own trees. This should help researchers in ecology and evolutionary biology in their everyday work, but may also permit the diffusion to a broader audience of our current knowledge of the evolutionary relationships linking all organisms

Visualizing Phylogenetic Trees: Algorithms And Visual Comparison Techniques

This thesis is about visualizing tree structured data. In particular, the emphasis is on visualizing the similarities and differences between pairs of trees. There are many research areas (such as biology, linguistics, chemistry and computer science) that use the tree as a basic data structure. The impetus for the work comes from the field of bioinformatics, where biologists construct complex phylogenetic trees to represent the evolution of species or genes. Once phylogenetic trees reveal potential interrelationships between examined species, the next step would be to validate the derived data

A reference guide for tree analysis and visualization

The quantities of data obtained by the new high-throughput technologies, such as microarrays or ChIP-Chip arrays, and the large-scale OMICS-approaches, such as genomics, proteomics and transcriptomics, are becoming vast. Sequencing technologies become cheaper and easier to use and, thus, large-scale evolutionary studies towards the origins of life for all species and their evolution becomes more and more challenging. Databases holding information about how data are related and how they are hierarchically organized expand rapidly. Clustering analysis is becoming more and more difficult to be applied on very large amounts of data since the results of these algorithms cannot be efficiently visualized. Most of the available visualization tools that are able to represent such hierarchies, project data in 2D and are lacking often the necessary user friendliness and interactivity. For example, the current phylogenetic tree visualization tools are not able to display easy to understand large scale trees with more than a few thousand nodes. In this study, we review tools that are currently available for the visualization of biological trees and analysis, mainly developed during the last decade. We describe the uniform and standard computer readable formats to represent tree hierarchies and we comment on the functionality and the limitations of these tools. We also discuss on how these tools can be developed further and should become integrated with various data sources. Here we focus on freely available software that offers to the users various tree-representation methodologies for biological data analysis

Selection Bias Tracking and Detailed Subset Comparison for High-Dimensional Data

The collection of large, complex datasets has become common across a wide variety of domains. Visual analytics tools increasingly play a key role in exploring and answering complex questions about these large datasets. However, many visualizations are not designed to concurrently visualize the large number of dimensions present in complex datasets (e.g. tens of thousands of distinct codes in an electronic health record system). This fact, combined with the ability of many visual analytics systems to enable rapid, ad-hoc specification of groups, or cohorts, of individuals based on a small subset of visualized dimensions, leads to the possibility of introducing selection bias--when the user creates a cohort based on a specified set of dimensions, differences across many other unseen dimensions may also be introduced. These unintended side effects may result in the cohort no longer being representative of the larger population intended to be studied, which can negatively affect the validity of subsequent analyses. We present techniques for selection bias tracking and visualization that can be incorporated into high-dimensional exploratory visual analytics systems, with a focus on medical data with existing data hierarchies. These techniques include: (1) tree-based cohort provenance and visualization, with a user-specified baseline cohort that all other cohorts are compared against, and visual encoding of the drift for each cohort, which indicates where selection bias may have occurred, and (2) a set of visualizations, including a novel icicle-plot based visualization, to compare in detail the per-dimension differences between the baseline and a user-specified focus cohort. These techniques are integrated into a medical temporal event sequence visual analytics tool. We present example use cases and report findings from domain expert user interviews.Comment: IEEE Transactions on Visualization and Computer Graphics (TVCG), Volume 26 Issue 1, 2020. Also part of proceedings for IEEE VAST 201

Implementation of an interactive visualization tool for analyzing dynamic hierarchies

Many real world examples can be found that deal with hierarchical data. Software systems typically consist of packages, directories, subdirectories, files, classes, and functions. Phylogenetic trees structure biological species into a hierarchical organization. Visualizing such static hierarchical data has been in focus of Information Visualization for many years. Visually encoding and understanding of evolving hierarchies still remains a challenging task. Since hierarchies may grow huge and may evolve over a long time producing many time steps, we make use of a side-by-side and aligned representation of Indented Pixel Tree Plots. To achieve a mental map preserving overview-based diagram we show the dynamics of a hierarchy by a static representation and illustrate the changes between subsequent hierarchies by special links. Interactive features make the data manipulable and navigable in all dimensions

트리 구조를 이용한 3차원 공간 내 데이터 시각화 연구

학위논문 (박사)-- 서울대학교 대학원 : 미술대학 디자인학부 디자인전공, 2019. 2. 김수정.Speculative visualization combines both data visualization methods and aesthetics to draw attention to specific social, political and environmental issues. The speculative data visualization project proposed in this work explores electronic waste trade and the environmental performance of various nations. Illegal trading of electronic waste without proper disposal and recycling measures has a severe impact on both human health and the environment. This trade can be represented as a network data structure. The overall environmental health and ecosystem vitality of those trading countries, represented by their Environmental Performance Index (EPI), can also give greater insight into this issue. This EPI data has a hierarchical structure. This work explores methods to visualize these two data sets simultaneously in a manner that allows for analytical exploration of the data while communicating its underlying meaning. This project-based design research specifically focuses on visualizing hierarchical datasets with a node-link type tree structure and suggests a novel data visualization method, called the data garden, to visualize these hierarchical datasets within a spatial network. This draws inspiration from networks found between trees in nature. This is applied to the illegal e-waste trade and environmental datasets to provoke discussion, provide a holistic understanding and improve the peoples awareness on these issues. This uses both analytical data visualization techniques, along with a more aesthetic approach. The data garden approach is used to create a 3D interactive data visualization that users can use to navigate and explore the data in a meaningful way while also providing an emotional connection to the subject. This is due to the ability of the data garden approach to accurately show the underlying data while also closely mimicking natural structures. The visualization project intends to encourage creative professionals to create both visually appealing and thought-provoking data visualizations on significant issues that can reach a mass audience and improve awareness of citizens. Additionally, this design research intends to cause further discussion on the role of aesthetics and creative practices in data visualizations.사변적 시각화(speculative visualization)는 데이터 시각화 방법과 미학을 결합하여 특정한 사회, 정치 및 환경 문제에 관심을 유도하는 것입니다. 제안한 사변적 데이터 시각화 프로젝트를 통해 다양한 국가의 전자 폐기물 거래와 환경 성과를 살펴봅니다. 적절한 처리와 재활용 조치가 이뤄지지 않은 전자폐기물의 불법 거래는 환경과 인간에 심각한 영향을 미칩니다. 이 거래는 네트워크 데이터 구조로 표현할 수 있습니다. 환경성과지수(EPI)를 통해 이 거래에 참여하는 국가들의 전반적인 환경 보건과 생태계 활력을 살펴보는 것은 이 문제에 더 깊은 통찰력을 제공할 수 있습니다. 이 환경성과지수는 계층 구조로 되어 있습니다. 이 연구는 데이터를 분석적으로 탐구할 수 있도록 하는 방법을 통해 두 가지 데이터를 동시에 시각화하고, 이를 통해 표면에 드러나지 않는 데이터의 의미를 전달하는 방법을 탐구합니다. 본 연구는 프로젝트를 기반으로 하는 디자인 연구로, 노드 링크 유형 트리 구조를 통해 계층적 데이터를 시각화하는 것에 중점을 두고 있습니다. 자연에서 발견할 수 있는 나무 간 네트워크에서 영감을 얻어 공간 네트워크에서 계층적 데이터 세트를 시각화합니다. 데이터 정원이라고 하는 이 새로운 데이터 시각화 방법을 불법 전자 폐기물 거래와 환경 데이터에 적용하여 토론을 유발하고 전체적인 이해를 제공하며 이러한 문제에 대한 사람들의 인식을 개선하고자 합니다. 이는 보다 미적인 접근과 분석적 데이터 시각화 기술을 모두 사용합니다. 데이터 정원을 통한 접근으로 삼차원 대화형 데이터 시각화를 만들 수 있습니다. 이 시각화를 통해 사용자는 데이터를 의미 있는 방식으로 살펴보는 동시에 주제와 감성적인 연결을 받을 수 있습니다. 이는 데이터 정원 방법이 데이터를 정확하게 보여주는 동시에 자연 구조를 면밀하게 모방하기 때문입니다. 본 시각화 프로젝트는 창의적인 전문가들이 중요한 문제에 대해 시각적으로 매력적이고 생각을 자극하는 데이터 시각화를 만들어 대중에게 도달하고 시민들의 인식을 향상할 수 있도록 권장합니다. 또한, 본 디자인 연구는 데이터 시각화에서 미학과 창조적인 실천의 역할에 대한 더 많은 논의를 유도하고자 합니다.Abstract I Table of Contents III List of Figures VI 1. Introduction 1 1.1 Research Background 2 1.2 Research Goal and Method 6 1.3 Terminology 9 2. Hierarchical Relationships: Trees 14 2.1 The History of Tree Diagrams 16 2.1.1 Significance of Trees 16 2.1.2 Aristotles Hierarchical Order of Life 19 2.1.3 Early Religious Depictions of Hierarchical Structures 22 2.1.4 Depicting Evolution 26 2.2 Tree Structures 29 2.3 Tree Layouts 31 3. Complex Relationships: Networks 34 3.1 Attributes of Networks 36 3.1.1 Interdependence and Interconnectedness 38 3.1.2 Decentralization 42 3.1.3 Nonlinearity 45 3.1.4 Multiplicity 46 3.2 Spatial Networks 46 3.3 Combining Tree Structures and Networks 48 4. Design Study Goals and Criteria 51 4.1 Objectives of the Design Study 71 4.2 Data Visualization Approaches 54 4.3 Criteria of Data Visualization 57 4.3.1 Aesthetics 58 4.3.2 Information Visualization Principles 62 4.3.2.1 Visual Cues in Data Visualization 62 4.3.2.2 Gestalt Principles 65 4.3.2.3 Increasing Efficiency of Network Visualizations 67 4.4 Case Study 70 5. Design Study: Data Garden Method 78 5.1 Concept of the Data Garden Structure 79 5.2 Data Garden Tree Structure 84 5.2.1 360°Vertical Branches 85 5.2.2 Break Point of the Branches 87 5.2.3 Aligning Hierarchy Levels 89 5.2.3.1 Design 01 – Extend Method 90 5.2.3.2 Design 02 – Collapse Method 91 5.2.4 Node Placement Technique 92 5.3 Conveying 3D Information 95 6. Design Study: Visualization Project 98 6.1 Theme 99 6.1.1 E-waste Trade 100 6.1.2 Environmental Performance Index 102 6.2 Visual Design Concept 104 6.3 Assigning Attributes 105 6.4 Visual Design Process 107 6.4.1 Leaf (Node) Design Process 107 6.4.1.1 Leaf Inspiration 107 6.4.1.2 Leaf Design 108 6.4.1.3 Leaf Area Calculation and Alignment 113 6.4.2 Stem (Branch) Design Process 116 6.4.3 Root (Link) Design Process 117 6.5 Interaction Design 118 6.5.1 Navigation 118 6.5.2 User Interface 119 6.5.3 Free and Detail Modes 120 6.5.4 Data Details 121 6.6 Visualization Renders 122 6.7 Exhibition 129 7. Conclusion 131 7.1 Conclusion 132 7.2 Limitations and Further Research 133 Bibliography 135 국문초록 (Abstract in Korean) 144Docto