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92

answers:

1

hi i m finding cosine similarity between documents ..i did like dis

D1=(8,0,0,1) where 8,0,0,1 are the tf-idf scores of the terms t1, t2, t3 , t4

D2=(7,0,0,1)

cos(theta) = (56 + 0 + 0 + 1) / sqrt(64 + 49) sqrt(1 +1 )

which comes out to be

cos(theta)= 5

now what do i evaluate from this value...i dont get it wat does cos(theta)=5 signify about the similarity between them...pls reply ..Am i doing things right ??????????..pls do reply guys.. will be thank ful to you..

+1  A: 

The denominator is wrong.

The cosine similarity is defined as

         D1 · D2
 sim = ———————————
        |D1| |D2|

Here

D1 · D2 = (7*8 + 0*0 + 0*0 + 1*1) = 57
           ______________________    __
   |D2| = √ 7^2 + 0^2 + 0^2 + 1^2 = √50
           ______________________    __
   |D1| = √ 8^2 + 0^2 + 0^2 + 1^2 = √65

So the similarity should be (57 / √(50 * 65)) = 0.999846142, not 5.

KennyTM
oh i neglected the zero values....how stupid of me...thanks kennyTM...thank u so much ...
jaskirat
@jaskirat: You did not neglect the zero values. You computed the |D1| and |D2| wrongly. There's nothing as √(7^2 + 8^2).
KennyTM
oh kk...well i took a reference from http://www.miislita.com/information-retrieval-tutorial/cosine-similarity-tutorial.html...
jaskirat
i m checking ur answer..but still i m not able to get the same answer as u showed (0.999846142)..
jaskirat
got it man...i was just cross checking the results..thanks kenny..enjoy
jaskirat