How to force Graphiz tool (dot, neato,...) to accept some initial node placement

Is there a way to force any Graphviz tool (dot, neato,...) to accept some initial node plac开发者_高级运维ement and keep them in this position, while placing the remaining nodes using its standard algorithm ?

I have tried to play with the "pos" node attribute in Neato, without success.

You can use

pos="x,y!"

The exclamation mark is important to do what you want !