open-connectome-classes / StatConn-Spring-2015-Info

introductory material
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vertex attribute/edge attribute/graph attribute #91

Open edunnwe1 opened 9 years ago

edunnwe1 commented 9 years ago

Given vertex and edge attributes, do we ever infer (or prove) graph attributes? Or are each of these sets of attributes defined completely independently? Related question: can edge attributes imply vertex attributes or vice versa? What if you were to have a directed graph of a neural circuit, say of the midget circuit in the retina, where you characterized edges as being either excitatory or inhibitory synapses in the presence of glutamate and you characterized vertices as being either ON or OFF [cells]. Perhaps you represent this as negative/positive weights for the edges and similarly negative or positive values for the vertices. I think, beginning with the knowledge of how cones respond to light, you could quickly see a relationship between the edge and vertex attributes in this circuit. Is this sort of relationship something that ever emerges in neuroscience graphs as an interesting result, or are graphs ever constructed explicitly with a relationship between v,e,g attributes in mind as a model that can exploit that relationship? Or would this be a sign of an ill-defined graph? If the former, and you wanted to demonstrate a relationship between attributes of one set and attributes of another, what would it take to demonstrate that relationship?

ghost commented 9 years ago

For the first part of your question, I think graph attributes are defined independently from vertex and edge attributes. If you only know the vertex is defined as either an excitatory or inhibatory cell you're not likely to be able to go backwards and say that this data came from the left eye (some random graph attribute) without further information about distribution, other descriptions. However you can look at the graph's network properties in order to try to infer a graph attribute. For example, detection of siezure based on the network pattern in several epilepsy patients. Perhaps you're confusing edge and vertex attributes with characteristics of the graph?

edunnwe1 commented 9 years ago

Thanks! I'm new to graph theory: can you elaborate on characteristics of a graph with a formal definition? Maybe formal definitions for attributes as well so I can understand the distinction that you are drawing?

dlee138 commented 9 years ago

I'd like some insight from this as well. Are you saying that characteristics of a graph =/= graph attributes but is an observation from a set of edge and vertex attributes? In other words, characteristics of a graph = an observable/statistically significant pattern between edge and vertex attributes that can happen to correspond to a graph attribute as well? For example, lets say you find a particular network pattern that is found in schizophrenic patients but not normal patients. Would the classification "has schizophrenia" be a graph attribute, while the pattern you observe be a "characteristic of the the graph" which happens to correlate to the graph attribute "has schizophrenia"?