Node absorption removes a node without affecting the overall global relationship of the rest of the nodes (i.e. the joint probability distribution).
This small demonstration of node absorption will show how it doesn’t effect the beliefs of the rest of the net. Open "Car_Diagnosis_2" from the Examples folder. Compile it with Network → Compile, and notice that the belief is 25.4% that “Spark Quality” is “good”. If you enter a finding of “dim” for node “Headlights”, the belief changes to 1.47%. Now select nodes “Main Fuse”, “Battery Age”, “Voltage at Plug” and “Spark Plugs”, and then click the toolbar button or choose Modify → Absorb Nodes. The selected nodes will be absorbed, links will be added and removed, and probability tables adjusted to maintain the global relationship. Now do Network → Compile, and observe the belief is 1.47% that “Spark Quality” is “good” as it was before the absorption. If you then do Network → Remove Findings, the belief changes to 25.4%, which is what it was in the old net before any findings were entered.
Link reversal changes the direction of a link without affecting the overall global relationship of the rest of the nodes (i.e. the joint probability distribution). Select a link and then click the toolbar button or choose Modify → Reverse Links. Netica may have to add extra links in order to maintain the joint probability distribution (or it may be able to remove some links).
See also Disconnecting
and Reconnecting Links
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