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Graphs are frequently drawn as node–link diagrams in which the vertices are represented as disks, boxes, or textual labels and the edges are represented as line segments, polylines, or curves in the Euclidean plane. Node–link diagrams can be traced back to the 13th century work of Ramon Llull, who drew diagrams of this type for complete graphs in order to analyze all pairwise combinations among sets of metaphysical concepts.

Graphs are frequently drawn as node–link diagrams in which the vertices are represented as disks, boxes, or textual labels and the edges are represented as line segments, polylines, or curves in the Euclidean plane. Node–link diagrams can be traced back to the 13th century work of Ramon Llull, who drew diagrams of this type for complete graphs in order to analyze all pairwise combinations among sets of metaphysical concepts.

图经常绘制成节点链接图，其中顶点可表示为圆盘、框或文本标签，边表示为'''<font color="#ff8000">欧几里德平面 Euclidean Plane</font>'''上的'''<font color="#ff8000">线段 Line Segments</font>'''、'''<font color="#ff8000">折线 Polylines</font>'''或曲线。节点链接图可以追溯到13世纪雷蒙 · 卢尔的作品，他为得到完全图，绘制了这种类型的图，以便分析形而上学概念集合之间的所有成对组合。

图经常绘制成节点链接图，其中顶点可以是为圆盘、框或文本标签，边表示为'''<font color="#ff8000">欧几里德平面 Euclidean Plane</font>'''上的'''<font color="#ff8000">线段 Line Segments</font>'''、'''<font color="#ff8000">折线 Polylines</font>'''或曲线。节点链接图可以追溯到13世纪雷蒙 · 卢尔的作品，他为得到完全图，绘制了这种类型的图，以便分析形而上学概念集合之间的所有成对组合。

In the case of directed graphs, arrowheads form a commonly used graphical convention to show their orientation; Upward planar drawing uses the convention that every edge is oriented from a lower vertex to a higher vertex, making arrowheads unnecessary.

In the case of directed graphs, arrowheads form a commonly used graphical convention to show their orientation; Upward planar drawing uses the convention that every edge is oriented from a lower vertex to a higher vertex, making arrowheads unnecessary.

在'''<font color="#ff8000">有向图 Directed Graphs</font>'''的情况下，'''<font color="#ff8000">箭头 Arrowheads</font>'''约定俗成的来显示它们的方向; '''<font color="#ff8000">向上平面绘图 Upward Planar Drawing</font>'''使用以下约定：每个边都从较低的顶点定向到较高的顶点，因此不需要箭头。

在'''<font color="#ff8000">有向图 Directed Graphs</font>'''的情况下，'''<font color="#ff8000">箭头 Arrowheads</font>'''我们规定它们的方向; '''<font color="#ff8000">在向上平面绘图中 Upward Planar Drawing</font>'''：每个边都从较低的顶点定向到较高的顶点，由此，就不再需要箭头指明方向。

Alternative conventions to node–link diagrams include adjacency representations such as circle packings, in which vertices are represented by disjoint regions in the plane and edges are represented by adjacencies between regions; intersection representations in which vertices are represented by non-disjoint geometric objects and edges are represented by their intersections; visibility representations in which vertices are represented by regions in the plane and edges are represented by regions that have an unobstructed line of sight to each other; confluent drawings, in which edges are represented as smooth curves within mathematical train tracks; fabrics, in which nodes are represented as horizontal lines and edges as vertical lines; and visualizations of the adjacency matrix of the graph.

Alternative conventions to node–link diagrams include adjacency representations such as circle packings, in which vertices are represented by disjoint regions in the plane and edges are represented by adjacencies between regions; intersection representations in which vertices are represented by non-disjoint geometric objects and edges are represented by their intersections; visibility representations in which vertices are represented by regions in the plane and edges are represented by regions that have an unobstructed line of sight to each other; confluent drawings, in which edges are represented as smooth curves within mathematical train tracks; fabrics, in which nodes are represented as horizontal lines and edges as vertical lines; and visualizations of the adjacency matrix of the graph.

节点链接图可被其他画图方式替代，包括邻接表示法，如'''<font color="#ff8000">圆填充 Circle Packings</font>'''，其中顶点表示为平面上不相交的区域，边表示为区域之间的邻接; '''<font color="#ff8000">交点表示 Intersection representations</font>'''，其中顶点由非相交的几何对象表示，而边线由其交点表示；可见性表示，其中顶点由平面中的区域表示，边由彼此无障碍视线的区域表示; 汇流图，其中边表示为数学轨迹上的光滑曲线; 织物，其中顶点表示为水平线，边表示为垂直线; 以及图形'''<font color="#ff8000">邻接矩阵 Adjiacency Matrix</font>'''的可视化结点。

节点链接图可被其他画图方式替代，包括邻接表示法，如'''<font color="#ff8000">圆填充 Circle Packings</font>'''，其中顶点表示为平面上不相交的区域，边表示为区域之间的邻接; '''<font color="#ff8000">交点表示 Intersection representations</font>'''，其中顶点由非相交的几何对象表示，而边由其交点表示；可见性：其中顶点由平面中的区域表示，边由彼此无障碍视线的区域表示; 汇流图，其中边表示为数学轨迹上的光滑曲线; 织物，其中顶点表示为水平线，边表示为垂直线; 以及图形'''<font color="#ff8000">邻接矩阵 Adjiacency Matrix</font>'''的可视化结点。

 

 

==Quality measures 质量度量==

==Quality measures 质量度量==