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Growing self-organizing map

Growing self-organizing map is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Growing self-organizing map rather than just read about it. In short: A growing self-organizing map (GSOM) is a growing variant of a self-organizing map (SOM). The GSOM was developed to address the issue of identifying a suitable map size in the SOM.

Growing self-organizing map — main illustration
Growing self-organizing map — illustration

Key takeaways

  • Growing self-organizing map belongs to computer science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Growing self-organizing map to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Growing self-organizing map from memory before moving on to harder problems.

Reference excerpt

A growing self-organizing map (GSOM) is a growing variant of a self-organizing map (SOM). The GSOM was developed to address the issue of identifying a suitable map size in the SOM. It starts with a minimal number of nodes (usually 4) and grows new nodes on the boundary based on a heuristic. By using the value called Spread Factor (SF), the data analyst has the ability to control the growth of the GSOM. All the starting nodes of the GSOM are boundary nodes, i.e. each node has the freedom to grow in its own direction at the beginning. (Fig. 1) New Nodes are grown from the boundary nodes. Once a node is selected for growing all its free neighboring positions will be grown new nodes. The figure shows the three possible node growth options for a rectangular GSOM.

The algorithm The GSOM process is as follows:

Initialization phase: Initialize the weight vectors of the starting nodes (usually four) with random numbers between 0 and 1. Calculate the growth threshold ( G T {\displaystyle GT} ) for the given data set of dimension D {\displaystyle D} according to the spread factor ( S F {\displaystyle SF} ) using the formula G T = − D × ln ⁡ ( S F ) {\displaystyle GT=-D\times \ln(SF)}

… excerpt ends here. Continue reading the full article.

Illustrations

Growing self-organizing map: Node growth options in GSOM: (a) one new node, (b) two new nodes and (c) three new nodes.
Node growth options in GSOM: (a) one new node, (b) two new nodes and (c) three new nodes.
Growing self-organizing map: Approximation of a spiral with noise by 1D SOM (the upper row) and GSOM (the lower row) with 50 (the first column) and 100 (the second column) nodes.  The Fraction of variance unexplained is: a) 4.68% (SOM, 50 nodes); b) 1.69% (SOM, 100 nodes); c) 4.20% (GSOM, 50 nodes); d) 2.32% (GSOM, 100 nodes). The initial approximation for SOM was equidistribution of nodes in a segment on the first principal component with the same variance as for the data set. The initial approximation for GSOM was the mean point.[1]
Approximation of a spiral with noise by 1D SOM (the upper row) and GSOM (the lower row) with 50 (the first column) and 100 (the second column) nodes. The Fraction of variance unexplained is: a) 4.68% (SOM, 50 nodes); b) 1.69% (SOM, 100 nodes); c) 4.20% (GSOM, 50 nodes); d) 2.32% (GSOM, 100 nodes). The initial approximation for SOM was equidistribution of nodes in a segment on the first principal component with the same variance as for the data set. The initial approximation for GSOM was the mean point.[1]

Worked examples

Example 1 — a first encounter with Growing self-organizing map

Start with the simplest possible case. Write down what Growing self-organizing map claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Growing self-organizing map before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Growing self-organizing map ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Growing self-organizing map

In research
Growing self-organizing map appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Growing self-organizing map in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Growing self-organizing map is common in secondary-school and first-year university syllabi. It links to neighbouring topics Artificial neural networks, Machine learning algorithms, so understanding it makes those chapters shorter.
In everyday life
Look for Growing self-organizing map outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Growing self-organizing map in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Growing self-organizing map means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Growing self-organizing map out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Growing self-organizing map in simple terms?

A growing self-organizing map (GSOM) is a growing variant of a self-organizing map (SOM). The GSOM was developed to address the issue of identifying a suitable map size in the SOM.

Why does Growing self-organizing map matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Growing self-organizing map?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Growing self-organizing map.

Tags

  • Artificial neural networks
  • Machine learning algorithms

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