# Distribution editor

Each node in a Bayesian network requires a probability distribution to be specified, conditioned on its parent nodes.

So for a node $A$, with parents $B,C$ the distribution to be specified is $P\left(A|B,C\right)$.

Distributions are made up from variables, not nodes. If nodes contain single variables, then nodes are equivalent to variables. However, if nodes contain multiple variables, then the distribution required contains the variables in the node, conditioned on the variables in the parent nodes. In the example above, if node $A$ contained the variables , $B$ contained  and $C$ contained just  then the distribution required for node $A$ would be $P\left(A1,A2|B1,B2,C1\right)$. ## Creating new distributions

If a node does not have a distribution assigned, click the New button to create one.

## Editing distributions

Once a distribution has been created for a node, numeric values can be entered in the grid(s) to define the distribution.

The shortcut key F2 can be used when a cell is selected, to put it into edit mode.

• For nodes with discrete variables, enter probability values, such that each parent combination sums to 1 (i.e. is stochastic). Counts/frequencies can also be entered, and then normalized to probability values by clicking the Normalize button. Random values can be assigned, ensuring the values are stochastic, by clicking the Randomize button.

• For continuous distributions, enter means/intercepts, covariances, and weights (regression coefficients).

## Deleting Distributions

If a node has a distribution assigned, the Delete button removes it, leaving a null distribution.

## Continuous Distributions

Continuous distributions in Bayes Server are represented by Conditional Linear Gaussian (CLG) distributions. If a continuous node has any discrete parents, then the probability table on the left allows selection of the Gaussian distribution that corresponds to the discrete combination selected.

## Temporal Distributions

Temporal nodes in a Dynamic Bayesian network, can have multiple distributions, that correspond to different times.

Each distribution can be selected by changing the Time drop down.

## Plot

A chart of continuous distributions can be generated by clicking the Plot button. This allows visualization of Gaussians and Mixtures of Gaussians, and also allows data to be added to the charts.

Zooming can be performed by dragging the mouse to select a region of the chart. 