www-ai.cs.tu-dortmund.de/de/LEHRE/SEMINARE/SS09/AKTARBEITENDESDM/FOLIEN/vortragItemSetsCompress.pdf
Item Sets that Compress - Arno Siebes Jilles Vreeken Matthijs van Leeuwen
Frequenz 2)
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Schwächen des naiven Ansatzes
Beispiel
CS1 = {{I1, I2}, {I1}, {I2}, {I3}} CS2 = {{I1, I2, I3}, {I1, I2}, {I1}, {I2}, {I3}} CS3 = {{I1, I2, I3}, {I1}, {I2}, {I3}}
Annahme: supp({I1, I2, I3}) [...] ) = suppdb(J)
Beispiel
Item Sets: {{I1 : 3} {I1, I2 : 2}{I1, I2, I3 : 2}︸ ︷︷ ︸{I1, I2, I3, I4 : 1}}
Closed Item Sets:{{I1 : 3}{I1, I2, I3 : 2}{I1, I2, I3, I4 : 1}}
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Kompression
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Kompression
Reduktion [...] Nachricht n1 n2 n3 n4
Code 0 10 110 111
10001111100100 → 10 0 0 111 110 0 10 0 → n2 n1 n1 n4 n3 n1 n2 n1
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Minimum Despription Length 2/3
Beispielcode ist optimal für W’keit(n1)= 1/2, W’keit(n2)=1/4, W …
