How to work out degree exponent for protein-protein interaction networks (cyctoscape, NetworkAnalyzer)?

Question

[Russellr11]

Hi

I’m working with a PPI network in cystoscape and have used NetworkAnalyzer for network parameters such as Node Degree Distribution, Shortest Path Distribution, Betweenness Centrality, etc.

When looking at the Node Degree Distribution; I can fit a line of power law and see, due to the negative slope, that my data fits the power law. However, I can’t for the life of me figure out how to work out the degree exponent.

I feel like I could be missing something very obvious. I can get the following information when fitting the power law; Power law of the form y=ax^b , where for my network a: 89.962 b:-0.855 correlation:0.734 R-squared: 0.754

Any help or advice provided would be extremely appreciated.

[russhh]

Isn't 'b' the degree-exponent?

[Russellr11]

Thank you for your reply!

[Jean-Karim Heriche]

Fitting a power law to the degree distribution means that the probability (or fraction) of nodes with degree n takes the form P(n) = a n^-b and the power law exponent is b. In your case, you used x^b so following the convention the power law exponent would be -b, i.e. 0.855 in your case.

[Russellr11]

I had a feeling I was missing something very simple and very obvious. Thank you for your reply!