cross-referencing dewey books and FAST subjects = more established categories!
Use OCLC thing, using the books you already have, to get a list of potential interests you already have.
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Heading Usage Count FAST ID
Digital filters (Mathematics) 672 893686
Signal processing–Mathematics 669 1118302
Image processing–Mathematics 669 967525
Computer graphics 63 872119
Computer vision 60 872687
Engineering 55 910312
Computer engineering 11 872078
Signal processing 3