Author Topic: Chain graphs  (Read 3022 times)

Offline DS

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Chain graphs
« on: October 06, 2015, 02:32:45 »
Hi
I am working with chain graphs and have heard that there exists some implementation for handling these in Hugin. From your homepage I can see that it is shown as a  feature (http://www.hugin.com/productsservices/products/feature-list) and there are also references to it when the .net format is explained in for example the API manual (example 13.5 to 13.7). The manual does however not explain how to set the data table for the potentials and when I play around with it myself I can't get it right. ???

So my questions are:
1. What functionality of chain graphs are supported by the Hugin GUI and the Hugin API?
2. If the API does not support direct adding and removing undirected edges (and setting corresponding potentials), how would one do this directly by manipulating the .net file. I.e. what would you write instead of dots in
Code: [Select]
potential (C3 C4 | C1 C2)
{
    data = ...
}
when handling a chain graph with the structure C1 -> C3 -- C4 <- C1 to get the right independence model and how can this model be used for inference using the Hugin inference engine?
3. Does it also exist support (in the inference engine etc.) for using continuous nodes when using chain graphs. I.e. for multivariate normal distributions over the nodes in the chain component?

Thanks beforehand for any answer! Great program!  :)

Offline Frank Jensen

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Re: Chain graphs
« Reply #1 on: October 06, 2015, 22:06:40 »
Hello,

1. Hugin only supports chain graphs that are specified using NET files.  These files can be loaded, and evidence can be entered for the nodes.  The evidence can be propagated, and beliefs can be retrieved.  But not much more than that.  Many API functions will return a "usage"-error if the network is a chain graph.

2. The data is a list of numbers in row-major order, as mentioned by Example 13.12 in the API manual.  Note that you can omit the (nested) parentheses.

3. There is no support for non-trivial (i.e., with more than one node) chain graph components containing CG nodes.

I hope this helps.