Md. Jawaherul Alam

• Ph.D.
• Assistant Project Scientist at University of California, Irvine

We describe bivariate cartograms , a technique specifically designed to allow for the simultaneous comparison of two geo-statistical variables. Traditional cartograms are designed to show only a single statistical variable, but in practice, it is often useful to show two variables (e.g., the total sales for two competing companies) simultaneously....

We study a problem motivated by rectilinear schematization of geographic maps. Given a biconnected plane graph G and an integer , does G have a strict-orthogonal drawing (i.e., an orthogonal drawing without edge bends) with at most k reflex angles per face? For , the problem is equivalent to realizing each face as a rectangle. We prove that the str...

In this paper we study threshold-coloring of graphs, where the vertex colors represented by integers are used to describe any spanning subgraph of the given graph as follows. A pair of vertices with a small difference in their colors implies that the edge between them is present, while a pair of vertices with a big color difference implies that the...

We study the algorithmic aspect of edge bundling. A bundled crossing in a drawing of a graph is a group of crossings between two sets of parallel edges. The bundled crossing number is the minimum number of bundled crossings that group all crossings in a drawing of the graph. We show that the bundled crossing number is closely related to the orienta...

We describe a graph visualization tool for visualizing Java bytecode. Our tool, which we call J-Viz, visualizes connected directed graphs according to a canonical node ordering, which we call the sibling-first recursive (SFR) numbering. The particular graphs we consider are derived from applying Shiver's k-CFA framework to Java bytecode, and our vi...

We study the algorithmic aspect of edge bundling. A bundled crossing in a drawing of a graph is a group of crossings between two sets of parallel edges. The bundled crossing number is the minimum number of bundled crossings that group all crossings in a drawing of the graph. We show that the bundled crossing number is closely related to the orienta...

Inspired by the artwork of Mark Lombardi, we study the problem of constructing orthogonal drawings where a small number of horizontal and vertical line segments covers all vertices. We study two problems on orthogonal drawings of planar graphs, one that minimizes the total number of line segments and another that minimizes the number of line segmen...

The class of doughnut graphs is a subclass of 5-connected planar graphs. It is known that a doughnut graph admits a straight-line grid drawing with linear area, the outerplanarity of a doughnut graph is 3, and a doughnut graph is -partitionable. In this paper we show that a doughnut graph exhibits a recursive structure. We also give an efficient al...

We study a problem motivated by rectilinear schematization of geographic maps. Given a biconnected plane graph G and an integer \(k\ge 0\), does G have a strict-orthogonal drawing with at most k reflex angles per face? For \(k=0\) the problem is equivalent to realizing each face as a rectangle. The problem can be reduced to a max-flow problem in so...

We study two variants of the problem of contact representation of planar graphs with axis-aligned boxes. In a cube-contact representation we realize each vertex with a cube, while in a proportional box-contact representation each vertex is an axis-aligned box with a prespecified volume. We show how to construct such representations representation f...

In a book embedding of a graph G, the vertices of G are placed in order along a straight-line called spine of the book, and the edges of G are drawn on a set of half-planes, called the pages of the book, such that two edges drawn on a page do not cross each other. The minimum number of pages in which a graph can be embedded is called the book-thick...

We study two variants of the problem of contact representation of planar graphs with axis-aligned boxes. In a cube-contact representation we realize each vertex with a cube, while in a proportional box-contact representation each vertex is an axis-aligned box with a prespecified volume. We present algorithms for constructing cube-contact representa...

We study contact representations of non-planar graphs in which vertices are represented by axis-aligned polyhedra in 3D and edges are realized by non-zero area common boundaries between corresponding polyhedra. We present a liner-time algorithm constructing a representation of a 3-connected planar graph, its dual, and the vertex-face incidence grap...

We study representations of graphs by contacts of circular arcs, CCA-representations for short, where the vertices are interior-disjoint circular arcs in the plane and each edge is realized by an endpoint of one arc touching the interior of another. A graph is (2, k)-sparse if every s-vertex subgraph has at most \(2s-k\) edges, and (2, k)-tight if...

Graph and cartographic visualization have the common objective to provide intuitive understanding of some underlying data. We consider a problem that combines aspects of both by studying the problem of fitting planar graphs on planar maps. After providing an NP-hardness result for the general decision problem, we identify sufficient conditions so t...

We study contact representations for graphs, which we call pixel representations in 2D and voxel representations in 3D. Our representations are based on the unit square grid whose cells we call pixels in 2D and voxels in 3D. Two pixels are adjacent if they share an edge, two voxels if they share a face. We call a connected set of pixels or voxels a...

Cartograms are used to visualize geographically distributed data by scaling the regions of a map (e.g., US states) such that their areas are proportional to some data associated with them (e.g., population). Thus the cartogram computation problem can be considered as a map deformation problem where the input is a planar polygonal map M and an assig...

Cartograms are maps in which areas of geographic regions (countries, states) appear in proportion to some variable of interest (population, income). Cartograms are popular visualizations for geo-referenced data that have been used for over a century and that make it possible to gain insight into patterns and trends in the world around us. Despite t...

We study contact representations of graphs in which vertices are represented by axis-aligned polyhedra in 3D and edges are realized by non-zero area common boundaries between corresponding polyhedra. We show that for every 3-connected planar graph, there exists a simultaneous representation of the graph and its dual with 3D boxes. We give a linear-...

We study representations of graphs by contacts of circular arcs, CCA-representations for short, where the vertices are interior-disjoint circular arcs in the plane and each edge is realized by an endpoint of one arc touching the interior of another. A graph is (2,k)-sparse if every s-vertex subgraph has at most 2s - k edges, and (2, k)-tight if in...

We study a variant of intersection representations with unit balls, that is, unit disks in the plane and unit intervals on the line. Given a planar graph and a bipartition of the edges of the graph into near and far sets, the goal is to represent the vertices of the graph by unit balls so that the balls representing two adjacent vertices intersect...

We study balanced circle packings and circle-contact representations for planar graphs, where the ratio of the largest circle's diameter to the smallest circle's diameter is polynomial in the number of circles. We provide a number of positive and negative results for the existence of such balanced configurations.

In 3D contact representations, the vertices of a graph are represented by 3D polyhedra and the edges are realized by non-zero-area common boundaries between corresponding polyhedra. While contact representations with cuboids have been studied in the literature, we consider a novel generalization of the problem in which vertices are represented by a...

We study a graph coloring problem motivated by a fun Sudoku-style puzzle. Given a bipartition of the edges of a graph into near and far sets and an integer threshold t, a threshold-coloring of the graph is an assignment of integers to the vertices so that endpoints of near edges differ by t or less, while endpoints of far edges differ by more than...

In smooth orthogonal layouts of planar graphs, every edge is an alternating sequence of axis-aligned segments and circular arcs with common axis-aligned tangents. In this paper, we study the problem of finding smooth orthogonal layouts of low edge complexity, that is, with few segments per edge. We say that a graph has smooth complexity k—for short...

A graph is 1-planar if it can be drawn in the plane such that each edge is crossed at most once. In general, 1-planar graphs do not admit straight-line drawings. We show that every 3-connected 1-planar graph has a straight-line drawing on an integer grid of quadratic size, with the exception of a single edge on the outer face that has one bend. The...

In a rectilinear dual of a planar graph vertices are represented by simple rectilinear polygons, while edges are represented by side-contact between the corresponding polygons. A rectilinear dual is called a cartogram if the area of each region is equal to a pre-specified weight. The complexity of a cartogram is determined by the maximum number of...

We study threshold-coloring of tilings of the plane by regular polygons, known as Archimedean lattices. We prove that some are threshold-colorable with constant number of colors while some require $O(\sqrt n)$ colors for a lattice of $n$ vertices. Using a threshold-coloring we can construct unit-cube contact representation for the colorable Archime...

In this paper we study threshold coloring of graphs, where the vertex colors represented by integers are used to describe any spanning subgraph of the given graph as follows. Pairs of vertices with near colors imply the edge between them is present and pairs of vertices with far colors imply the edge is absent. Not all planar graphs are threshold-c...

In a contact representation of a planar graph, vertices are represented by interior-disjoint polygons and two polygons share a non-empty common bound-ary when the corresponding vertices are adjacent. In the weighted version, a weight is assigned to each vertex and a contact representation is called propor-tional if each polygon realizes an area pro...

The class doughnut graphs is a subclass of 5-connected planar graphs. It is known that a doughnut graph admits a straight-line grid drawing with linear area, the outerplanarity of a doughnut graph is 3, and a doughnut graph is k-partitionable. In this paper we show that a doughnut graph exhibits a recursive structure. We also give an efficient algo...

In a proportional contact representation of a planar graph, each vertex is represented by a simple polygon with area proportional to a given weight, and edges are represented by adjacencies between the corresponding pairs of polygons. In this paper we first study proportional contact representations that use rectilinear polygons without wasted area...

We study contact representations for planar graphs, with vertices represented by simple polygons and adjacencies represented by point-contacts or side-contacts between the corresponding polygons. Specifically, we consider proportional contact representations, where pre-specified vertex weights must be represented by the areas of the corresponding p...

A layered drawing of a tree T is a planar straight-line drawing of T, where the vertices of T are placed on some horizontal lines called layers. A minimum-layer drawing of T is a layered drawing of T on k layers, where k is the minimum number of layers required for any layered drawing of T. In this paper we give a linear-time algorithm for obtainin...

A layered drawing of a tree T is a planar straight-line drawing of T, where the vertices of T are placed on some horizontal lines called layers. A minimum-layer drawing of T is a layered drawing of T on k layers, where k is the minimum number of layers required for any layered drawing of T. In this paper we give a linear-time algorithm for obtainin...

A straight-line grid drawing of a planar graph G is a drawing of G on an integer grid such that each vertex is drawn as a grid point and each edge is drawn as a straight-line segment without edge crossings. Any outerplanar graph of n vertices with maximum degree d has a straight-line grid drawing with area O(dnlogn). In this paper, we introduce a s...

A straight-line grid drawing of a plane graph G is a planar drawing of G, where each vertex is drawn at a grid point of an integer grid and each edge is drawn as a straight-line segment. The height, width and area of such a drawing are respectively the height, width and area of the smallest axis-aligned rectangle on the grid which encloses the draw...

An upward drawing of a rooted tree T is a planar straight-line drawing of T where the vertices of T are placed on a set of horizontal lines, called layers, such that for each vertex u of T, no child of u is placed on a layer vertically above the layer on which u has been placed. In this paper we give a linear-time algorithm to obtain an upward draw...

A straight-line grid drawing of a plane graph G is a planar drawing of G, where each vertex is drawn at a grid point of an integer grid and each edge is drawn as a straight-line segment. The height, width and area of such a drawing are respectively the height, width and area of the smallest axis-aligned rectangle on the grid which encloses the draw...

A straight-line grid drawing of a planar graph G is a drawing of G on an integer grid such that each vertex is drawn as a grid point and each edge is drawn as a straight-line segment without edge crossings. Any outerplanar graph of n vertices with the maximum degree d has a straight-line grid drawing with area O(dn logn). In this paper, we introduc...

A minimum segment drawing Γ of a planar graph G is a straight line drawing of G that has the minimum number of segments among all straight line drawings of G. In this paper, we give a linear-time algorithm for computing a minimum segment drawing of a series-parallel graph with the maximum degree three.To the best of our knowledge, this is the first...

In a planar straight-line drawing of a tree T on k layers, each vertex is placed on one of k horizontal lines called layers and each edge is drawn as a straight-line segment. A planar straight-line drawing of a rooted tree T on k layers is called an upward drawing of T on k layers if, for each vertex u of T, no child of u is placed on a layer verti...