The NETDRAW Procedure

As explained in the previous section, the layout of the network is determined by the procedure in terms of x and y coordinates on a grid as shown in Figure 9.7. The distance between nodes and the width and height of each node is determined by the values of the format control options: XBETWEEN= , YBETWEEN= , BOXHT= , and BOXWIDTH= . Note that if the ROTATETEXT option is specified (in graphics mode), then the definitions of the BOXHT= and BOXWIDTH= options are reversed.

The amount of information that is displayed within each node is determined by the variables specified by the ID= option, the number of default variables found in the Network data set, and whether the NOLABEL and NODEFID options are specified. The values of the variables specified by the ID= option are placed within each node on separate lines. If the NOLABEL option is in effect, only the values of the variables are written; otherwise, each value is preceded by the name of the ID variable truncated to three characters. Recall from the section Syntax: NETDRAW Procedure that, in addition to the variables specified using the ID= option, the procedure also displays additional variables. These variables are displayed below the variables explicitly specified by the ID= option, in pre-determined relative positions within each node (see Table 9.3.)

Note: If a node is identified as a successor (through a SUCCESSOR variable) and is never identified with the ACTIVITY variable, the ID values for this node are never defined in any observation; hence, this node will have missing values for all the ID variables.

If the SHOWSTATUS option is specified and the Network data set contains progress information (in either the STATUS variable or the A_START and A_FINISH variables), the procedure appropriately marks each node referring to activities that are completed or in progress. See Example 9.8 for an illustration of the SHOWSTATUS option.

The features just described pertain to all three modes of the procedure. In addition, there are options to control the format of the display that are specific to the mode of invocation of the procedure. For graphics quality network diagrams, you can choose the color and pattern used for each node separately by specifying a different pattern number for the PATTERN variable, identified in the ACTNET statement (for details, see the section Graphics Version). For line-printer or full-screen network diagrams, the FORMCHAR= option enables you to specify special boxing characters that enhance the display; for full-screen network diagrams, you can also choose the color of the nodes using the PATTERN= option.

By default, all arcs are drawn along the center track between two consecutive nodes. The SEPARATEARCS option, which is available in the graphics version, separates arcs in the same corridor by drawing them along separate tracks, thus preventing them from being drawn on top of each other.

If the network fits on one page, it is centered on the page; in the graphics mode, you can use the NOVCENTER option to prevent centering in the vertical direction so that the network is drawn immediately below the title. If the network cannot fit on one page, it is split onto different pages appropriately. See the section Page Format for a description of how the pages are split.