Free body diagrams close free body diagramA simplified drawing of an object or system showing the forces acting on it. The forces are shown acting away from the centre of a box or dot. are used to ...

This example illustrates the use of PROC NETDRAW to draw two networks ... Three ID variables are used to specify the text that is to be placed within each node. The flow diagram is shown in Output ...

Dia isn't the only alternative to Visio out there (I've also told you about Project Draw, an online app, for example) but Dia is small, smart, and free -- definitely worthy of your attention.