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Text as Data and NLP for Finance / Finance lexicons and disclosures

Embeddings

A bag of words gives every type its own axis. Two filings that never share a string have inner product zero, even when one says “impairment” and the other says “write-down” in the same local context. An embedding is a dense vector for the word, learned so that words which keep similar company land near each other. For the equity-event feature, the measurement decision is whether financial tone lives in exact list hits or in contextual similarity. The implementation is a set of four design choices. The validation deliverable is performance on the tone task, not a high score on a generic analogy test.
Learning objectives. By the end of this note you should be able to:
  • state the distributional hypothesis in the form used for embeddings;
  • distinguish a one-hot type from a KK-dimensional embedding with KK below the vocabulary size;
  • name the four design choices and the CBOW versus skip-gram objectives;
  • say how a document vector is obtained, and which evaluation is the one that matters for a 10-K tone feature.

In this lesson

  1. From one-hot types to distributed vectors
  2. How the vectors are estimated
  3. From words to a filing
  4. Validation
  5. What you must record before the vector is a feature

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