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ioam / topographica

A general-purpose neural simulator focusing on topographic maps.
topographica.org
BSD 3-Clause "New" or "Revised" License
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the mathematical form of elongated Gaussian pattern #682

Closed kalok87 closed 6 years ago

kalok87 commented 6 years ago

Dear developers,

Which of the following mathematical forms is used for Gaussian pattern performed in Retina?

1) 1/(2Pi) Exp[-(x^2 + y^2/a^2)] 2) 1/(2Pia) * Exp[-(x^2 + y^2/a^2)]

where the a is the aspect ratio, and Sigma = 1 for simplification. Compare to the first one, the second expression above also normalize the y-component in the Gaussian pattern which leaves a in the denominator.

jbednar commented 6 years ago

This is a question about ImaGen, not Topographica per se, but both of these projects are open source, so you can and should check the code yourself whenever you have questions like that:

https://github.com/ioam/imagen/blob/master/imagen/patternfn.py#L39

https://github.com/ioam/imagen/blob/master/imagen/__init__.py#L75

kalok87 commented 6 years ago

Dear Prof. Bednar. Thank you for your replying. I thought the packages are in the topo/pattern directory due to the .ty (from topo.pattern import gaussian) file but I cannot find it so I ask it here. Thank you for the help.

jbednar commented 6 years ago

Yes, that's confusing; topo.patterns was where the patterns were originally, but we split them out into the separate ImaGen project so that they could be reused in other contexts. We kept the alias topo.pattern so that old code would keep working, but it's confusing that the code isn't really there!