Talk:Generative topographic map

Contradiction with Self-organizing map article

The following appears to contradict what is said in Self-organizing map about topology preservation."A key difference between the GTM and the SOM is that the nodes in the SOM can wander around at will; GTM nodes are constrained by the allowable transformations and the probabilities on those transformations. If the deformations are well-behaved the topology of the latent space is preserved.."

Exactly which passage in SOM do you think contradicts the cited one?

In the SOM the best-matching unit (BMU) is determined in each step/iteration. Consequently it can wander around in the sequence of learning iterations.

Citation from Self-organizing map:

'When a training example is fed to the network, its Euclidean distance to all weight vectors is computed. The neuron with weight vector most similar to the input is called the best matching unit (BMU).' —Preceding unsigned comment added by 134.245.67.180 (talk) 14:45, 11 August 2008 (UTC)

Biased comparison with SOM?

I think that the comparison with SOM is a bit biased. Cited advantages are:

1-it explicitly formulates a density model over the data.

  Does this really constitutes an advantage? Why?

2-it uses a cost function that quantifies how well the map is trained.

  SOM also has its ways to quantify errors, namely the quantization error and the topographical error.

3-it uses a sound optimization procedure (EM algorithm).

  This may be the main (or the only one?) advantage of GTM over SOM. (EPleite (talk) 20:13, 1 November 2010 (UTC))

(seconded - the strict density model may be an advantage in some situations, but an entire class of non-parametric models exists bc some situations are benefitted by a less constrained approach) — Preceding unsigned comment added by 198.233.238.206 (talk) 15:38, 10 November 2015 (UTC)

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