The Annotate facility enables you to enhance graphics output produced by PROC NETDRAW. To use this facility, you must create an Annotate data set, which contains a set of graphics commands that can be superimposed on the network diagram. This data set has a specific format and must contain key variables as described in SAS/GRAPH Software: Reference. The chapter entitled "The Annotate Data Set" lists the variables that are required in this data set and explains the coordinate systems used by the Annotate facility. The present section explains the use of data coordinates specifically with reference to the NETDRAW procedure.

When annotating a graph produced by any of the graphics procedures, it is helpful to use data coordinates that refer to the data values corresponding to the graph that is being annotated. For example, if you want to label a particular node of a network diagram with additional text, you can position the text accurately if you use data coordinates instead of screen coordinates. With respect to PROC NETDRAW, the Annotate facility uses the _X_ and _Y_ values in the Layout data set as the basis for the data coordinate system. To use this feature, you can invoke PROC NETDRAW (with the NODISPLAY option, if necessary) for the given network to produce the Layout data set that contains the _X_ and _Y_ coordinates for each node of the network. This data set can then be used to create the required Annotate data set containing the graphics commands positioning the primitives appropriately on the diagram using the data coordinates. See Example 9.16 and Example 9.17 for illustrations of this feature.

Note:The data coordinate system enables you to annotate the graph even if it spans multiple pages. However, each annotation must be entirely contained within a given page. For example, you cannot annotate a line on the network diagram that runs from one page of the diagram to another.