# EM

## (Tutorial)

Consider the Bayesian belief network (Bbn) from Adaptation tutorial. Figure 1 shows the current distribution probability for the net.

Figure 1: Current Distribution Probabilities

Now go back to "edit mode" and set all the conditional distribution probability to 1 except "Tuberculosis or cancer" node. Switch back to "run mode" and push "EM-Learning" icon. The EM-Learning icon is shown in figure 2.

Figure 2: The EM-Learning Icon

When the icon is pushed the EM learning window appears. Note that the field "Convergence threshold" response to the log-likelihood. Push "Select File" button and choose a file from which the conditional distribution probabilities must be computed. When the file is selected the "OK" button appears as shown in figure 3.

Figure 3: The EM-Learning Window

Pushing the "OK" button starts the EM-algorithm. Based on the case set given in the file the EM-algorithm computes the conditional distribution probability for each node. Figure 4 shows the new conditional distribution probability based on asia.dat file.

Figure 4: The New Conditional Distribution Probabilities

| HUGIN Expert A/S | , 2000

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