V-structure: Difference between revisions
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In graphical models, a '''v-structure''' is a set of three nodes in a graph such that there are two converging arrows and the tails of the arrows are not connected by an arrow.<ref>Judea Pearl. ''Causality''. p. 19.</ref><ref>https://ermongroup.github.io/cs228-notes/representation/directed/</ref> For example, <math>X \rightarrow Z \leftarrow Y</math> is a v-structure. | In graphical models, a '''v-structure''' is a set of three nodes in a graph such that there are two converging arrows and the tails of the arrows are not connected by an arrow.<ref>Judea Pearl. ''Causality''. p. 19.</ref><ref>[https://ermongroup.github.io/cs228-notes/representation/directed/ "Bayesian networks"]. Retrieved September 21, 2018.</ref> For example, <math>X \rightarrow Z \leftarrow Y</math> is a v-structure because the arrows converge at <math>Z</math> and the nodes <math>X</math> and <math>Y</math> are not directly connected. | ||
The middle node in a v-structure is called a [[collider]]. (?) | The middle node in a v-structure is called a [[collider]]. (?) | ||
Some authors seem to distinguish between a v-structure and an immoral v-structure. In this case, "v-structure" seems to only mean that there is a collision, and the "immoral" means the parents are not directly connected.<ref>Su-In Lee. [https://courses.cs.washington.edu/courses/cse515/11sp/class2-bayesnet.pdf "Bayesian Network Representation"]. University of Washington CSE 515, Statistical Methods, Spring 2011. p. 14 (slide 27). March 30, 2011. Retrieved September 21, 2018.</ref> | Some authors seem to distinguish between a v-structure and an immoral v-structure. In this case, "v-structure" seems to only mean that there is a collision, and the "immoral" means the parents are not directly connected.<ref>Su-In Lee. [https://courses.cs.washington.edu/courses/cse515/11sp/class2-bayesnet.pdf "Bayesian Network Representation"]. University of Washington CSE 515, Statistical Methods, Spring 2011. p. 14 (slide 27). March 30, 2011. Retrieved September 21, 2018.</ref><ref>Dave Essary. [https://people.cs.pitt.edu/~milos/courses/cs3710/Lectures/Class4.pdf "Bayesian Networks Representation"]. p. 15. Retrieved September 21, 2018.</ref> | ||
==Terminology== | ==Terminology== | ||
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Latest revision as of 00:26, 15 January 2019
In graphical models, a v-structure is a set of three nodes in a graph such that there are two converging arrows and the tails of the arrows are not connected by an arrow.[1][2] For example, is a v-structure because the arrows converge at and the nodes and are not directly connected.
The middle node in a v-structure is called a collider. (?)
Some authors seem to distinguish between a v-structure and an immoral v-structure. In this case, "v-structure" seems to only mean that there is a collision, and the "immoral" means the parents are not directly connected.[3][4]
Terminology
why is this thing called a v-structure? because it looks like a letter V if the two parents are drawn above the common child?
References
- ↑ Judea Pearl. Causality. p. 19.
- ↑ "Bayesian networks". Retrieved September 21, 2018.
- ↑ Su-In Lee. "Bayesian Network Representation". University of Washington CSE 515, Statistical Methods, Spring 2011. p. 14 (slide 27). March 30, 2011. Retrieved September 21, 2018.
- ↑ Dave Essary. "Bayesian Networks Representation". p. 15. Retrieved September 21, 2018.