The NETDRAW Procedure

Getting Started: NETDRAW Procedure

The first step in defining a project is to make a list of the activities in the project and determine the precedence constraints that need to be satisfied by these activities. It is useful at this stage to view a graphical representation of the project network. In order to draw the network, you specify the nodes of the network and the precedence relationships among them. Consider the software development project that is described in the "Getting Started" section of Chapter 2, "The CPM Procedure." The network data are in the SAS data set SOFTWARE, displayed in Figure 7.1.

Software Project Data Set SOFTWARE Obs descrpt duration activity succesr1 succesr2 1 Initial Testing 20 TESTING RECODE   2 Prel. Documentation 15 PRELDOC DOCEDREV QATEST 3 Meet Marketing 1 MEETMKT RECODE   4 Recoding 5 RECODE DOCEDREV QATEST 5 QA Test Approve 10 QATEST PROD   6 Doc. Edit and Revise 10 DOCEDREV PROD   7 Production 1 PROD

Figure 7.1: Software Project

The following code produces the network diagram shown in Figure 7.2:

  
    pattern1 v=e c=green; 
    title 'Software Project'; 
    proc netdraw graphics data=software; 
       actnet / act=activity 
                succ=(succesr1 succesr2) 
                pcompress separatearcs; 
       run;
 

Figure 7.2: Software Project

The procedure determines the placement of the nodes and the routing of the arcs on the basis of the topological ordering of the nodes and attempts to produce a compact diagram. You can control the placement of the nodes by specifying explicitly the node positions. The data set SOFTNET, shown in Figure 7.3, includes the variables _X_ and _Y_, which specify the desired node coordinates. Note that the precedence information is conveyed using a single SUCCESSOR variable unlike the data set SOFTWARE, which contains two SUCCESSOR variables.

Software Project Data Set SOFTNET Obs descrpt duration activity succesor _x_ _y_ 1 Initial Testing 20 TESTING RECODE 1 1 2 Meet Marketing 1 MEETMKT RECODE 1 2 3 Prel. Documentation 15 PRELDOC DOCEDREV 1 3 4 Prel. Documentation 15 PRELDOC QATEST 1 3 5 Recoding 5 RECODE DOCEDREV 2 2 6 Recoding 5 RECODE QATEST 2 2 7 QA Test Approve 10 QATEST PROD 3 3 8 Doc. Edit and Revise 10 DOCEDREV PROD 3 1 9 Production 1 PROD   4 2

Figure 7.3: Software Project: Specify Node Positions

The following code produces a network diagram (shown in Figure 7.4) with the new node placement:

  
    title2 h=1.5 'Controlled Layout'; 
    proc netdraw graphics data=softnet; 
       actnet / act=activity 
                succ=(succesor) 
                pcompress; 
       run;
 

Figure 7.4: Software Project: Controlled Layout

Software Project Project Schedule descrpt activity succesr1 succesr2 duration E_START E_FINISH L_START L_FINISH T_FLOAT F_FLOAT Initial Testing TESTING RECODE   20 01MAR04 20MAR04 01MAR04 20MAR04 0 0 Prel. Documentation PRELDOC DOCEDREV QATEST 15 01MAR04 15MAR04 11MAR04 25MAR04 10 10 Meet Marketing MEETMKT RECODE   1 01MAR04 01MAR04 20MAR04 20MAR04 19 19 Recoding RECODE DOCEDREV QATEST 5 21MAR04 25MAR04 21MAR04 25MAR04 0 0 QA Test Approve QATEST PROD   10 26MAR04 04APR04 26MAR04 04APR04 0 0 Doc. Edit and Revise DOCEDREV PROD   10 26MAR04 04APR04 26MAR04 04APR04 0 0 Production PROD     1 05APR04 05APR04 05APR04 05APR04 0 0

Figure 7.5: Software Project Schedule

While the project is in progress, you may want to use the network diagram to show the current status of each activity as well as any other relevant information about each activity. PROC NETDRAW can also be used to produce a time-scaled network diagram using the schedule produced by PROC CPM. The schedule data for the software project described earlier are saved in a data set, INTRO1, which is shown in Figure 7.5.

To produce a time-scaled network diagram, use the TIMESCALE option in the ACTNET statement, as shown in the following program. The MININTERVAL= and the LINEAR options are used to control the time axis on the diagram. The ID=, NOLABEL, and NODEFID options control the amount of information displayed within each node. The resulting diagram is shown in Figure 7.6.

  
    title2 h=1.5 'Time-Scaled Diagram'; 
    proc netdraw graphics data=intro1; 
       actnet / act=activity succ=(succ:) 
                separatearcs pcompress htext=2 
                timescale linear frame mininterval=week 
                id=(activity duration) nolabel nodefid; 
       run;
 

Figure 7.6: Software Project: Time-Scaled Network Diagram

Several other options are available to control the layout of the nodes, the appearance of the network, and the format of the time axis. For projects that have natural divisions, you can use the ZONE= option to divide the network into horizontal zones or bands. For networks that have an embedded tree structure, you can use the TREE option to draw the network like a tree laid out from left to right, with the root at the left edge of the diagram; in graphics mode, you can obtain a top-down tree with the root at the top of the diagram. For cyclic networks you can use the BREAKCYCLE option to enable the procedure to break cycles. All of these options are discussed in detail in the following sections.