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

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Non categorical model for Z (Bock) #128

Open dlee138 opened 9 years ago

dlee138 commented 9 years ago

Has anyone tried using a non-categorical model for Z for the Bock paper assignment? Although we discussed that SBM doesn't work - I want to get a sense of what other models can be used for Z other than merely categorizing Z as 8 or "x" number of categories.

jtmatterer commented 9 years ago

I proposed the following model after class:

The sample space is (A,Y,X) \in {0,1}^{n\times n} \times {0,1}^n \times [-\pi,\pi]^{n\times n \times n}.

Here, A is the adjacency matrix for the graph, Y is whether the neuron is excitatory or inhibatory, and X is a difference between two orientation preferences. Specifically, we can define the model so that

X_{uvw} = z_u - z_v if u~w, v~w, u and v are excitatory and w is inhibatory 0 otherwise,

where z_u is the orientation preference for neuron u. By conditioning on the graph and neuron type, we can decompose the model

F{A,Y,X} = F{X|A,Y} F_{A,Y}.

Then making the assumption that the differences in orientation preference are independent for such occurrences in the graph, we can factor the model

F{A,Y,X} = \prod F{X{uvw}|A,Y} F{A,Y}.

Phrased in terms of this model, the statistical test from Bock is whether F{X{uvw}|A,Y} is the uniform distribution or not.

I apologize to anyone who had difficulty reading the LaTeX. Sidenote: does anyone know if there is a good way to embed LaTeX code into github comments? I googled the question, but couldn't find anything satisfactory.

imichaelnorris commented 9 years ago

@kurtosis312 MathJax would be a nice way to format the Latex in the browser, but upon reading github support emails, it appears that github does not currently support LaTeX formatting. To use MathJax, you would need to load the JavaScript library, which you probably can't do (I think they did allow Latex in the past, but there are some security issues).

On a side note, if I get the time, it would be somewhat trivial for me to create a website that could host little snippets of LaTeX using MathJax, that could render them so that in situations like this, you could just post a URL and when you click it, it displays some LaTeX.