# Independant Component Analysis PCA works to maximize variance, ICA assumes that the features are mixtures of independant sources. It tries to isolate these independant sources that are mixed in this dataset. Ex: say you only have 3 recordings of a piano, cello and tv that were played but not playing the same musique: ![](https://846345873-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LagOeJ2nL90MQERwhxy%2F-Ln41l11hC8FBWgb6AAk%2F-Ln46xxhOh1wekFAjCFR%2Fimage.png?alt=media\&token=b3f82de9-8a13-41c5-8a20-e57a27aedefc) With ICA, it is possible to retrieve each tune independantly. Blind source separation ![](https://846345873-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LagOeJ2nL90MQERwhxy%2F-Ln41l11hC8FBWgb6AAk%2F-Ln47OMZba4U8RH4j8Iy%2Fimage.png?alt=media\&token=f1e771a3-36fe-409f-88b8-a8a7c13cd4ff) ### Algorithm ![](broken-reference) g is tanh function, but can be other functions, we have different options. The decorrelation matrix is W. ICA Assumptions: The components are statistically independant. Components have non Gaussian distributions. Very important. The algo tries to maximise the non gaussianity. One way to calculate this is the w+ above. It is called negentropy. w+ is how we approximate it. Applications Brain scan data, retail earnings to find patterns. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://julienbeaulieu.gitbook.io/wiki/sciences/machine-learning/unsupervised-learning/dimensionality-reduction/independant-component-analysis.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.