Chapter 11. Handling a graph

Table of Contents

Browsing a graph through its nodes.
Selecting nodes
Graph parameters
Using nomenclatures
Modifying the value of graph's attributes and saving a new graph

As we saw before, graphs enable to represent structured data with nodes and associated attributes. Graphs also have global attributes defining characteristics shared by all nodes, as for example voxels size. Nodes also can be linked by relations. This is used in sulci graphs to represent several units extracted from a sulcus. You can see these relations by selecting the neighbours of a node.

Graph nodes contain structures labels (for sulci and ROI graphs), which may be stored in two possible attributes, name and label. These two attributes have the same role : naming a node. Then, it is possible to make a link with a nomenclature file in order to associate a color to each value of attributes name or label.

So, what's the use having 2 different attributes with the same role ? In some case, we need a double identification. For example, in a automatic sulci recognition, nodes are renamed by computer experts. When consulting the results, you might want to rename a sulcus and keep the original identification, which is highly recommended.

Browsing a graph through its nodes.

Follow these steps :

  • Put the graph in a 3D window.

  • Right click on the window and select the menu View / select objects. A browser window opens.

  • Then, you can select a node in the browser window, it will be highlighted in the 3D window.

  • Conversely, when the selection control is active in a 3D window, clicking on a node in the 3D view will select it, both in 3D views and in browser windows. See next section for details.

If you don't want to see all the nodes of the graph because it is a big graph and you want to see only chosen nodes, you can use the object menu Display -> Add without nodes available by right clicking on the graph. Selects a window and use this feature, the graph will be loaded in the window but its node won't be visible. If there is no opened window, Anatomist will open a new 3D window and load the graph in it. If there are several windows and none is selected, Anatomist will load the graph in each window. Then, you can use the menu View / select objects to select the nodes you want to see.