Biological measurements and data matrices
A data matrix organizes rows as observations and columns as features.
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A data matrix organizes rows as observations and columns as features. In gene expression a row may be a sample and columns genes; in EEG a row may be a recording window and columns signal features. Metadata describes how each observation was collected and what label, if any, it has. Different technologies measure different parts of biology, so units and detection limits matter.
Worked example
A 12 by 500 expression table contains 12 samples and 500 gene features. The treatment label belongs in metadata linked by sample ID, not disguised as a gene.