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  "body": "\n## Summary\n\nA sparse matrix is a matrix in which most entries are zero.\nSuch matrices are stored by listing only the nonzero entries with their positions, which saves memory.\nAlgorithms that skip the zeros can be much faster than algorithms for general, dense matrices.\nLarge sparse matrices arise from networks, from discretised differential equations and from many problems in data science.\n\n## Explanations\n\n### L1 human\n\nThink of a matrix that records which of a million people know each other.\nEach person knows only a few hundred others, so almost all of the trillion entries are zero.\nStoring all entries would be wasteful; it is enough to store, for each nonzero entry, its row, its column and its value.\nThe [[tridiagonal|DARX1KZRHZ]] and [[band|Z58FRZCF8P]] matrices are simple examples of sparse matrices.\n",
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