1 / 5

CVV Example

CVV Example. DF i,j Assumption. If we assume that DF i,j = the number of documents in collection c i containing term t j : A = DF i,j / N i proportion of docs in c i containing term t j B = Sum k!=i |C| (DF k,j ) / Sum k!=i |C| (N k )

whitley
Download Presentation

CVV Example

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CVV Example

  2. DFi,j Assumption • If we assume that DFi,j = the number of documents in collection ci containing term tj : • A = DFi,j / Ni • proportion of docs in ci containing term tj • B = Sumk!=i|C|(DFk,j) / Sumk!=i|C|(Nk) • proportion of docs not in ci containing term tj • not the same as Sumk!=i|C| (DFk,j/Nk) • A + B != proportion of all docs containing tj • see example on next page

  3. CVV Example (for one term tj) • Given: |C| = 3, DF1..3,j={1,2,0}, N1..3={2,4,4} • c1: A=1/2, B = (2+0) / (4+4) = 2/8 = 1/4A+B = 1/2 + 1/4 = 3/4, CV1,j = (1/2)/(3/4) = 2/3 • prop of all docs containing tj = (1+2) / (2+4+4) = 3/10 • c2: A = 2/4=1/2, B = (1+0) / (2+4) = 1/6CV2,j = (1/2) / (1/2 + 1/6) = (1/2) / (4/6) = 3/4 • c3: A = 0/4 = 0, B = (1+2) / (2+4) = 3/6 = 1/2CV3,j = 0 / (0 + 1/2) = 0 • So, CV1..3,j = {2/3, 3/4, 0}

  4. CVV Example (cont) • CV1..3,j = {2/3, 3/4, 0} [from previous page] • avgCVj = Sumi=1|C|(CVi,j) / |C| = (2/3 + 3/4 + 0) / 3 = .472 • CVVj = Sumi=1|C|(CVi,j - avgCVj)2 / |C| = ((.667-.472)2 + (.75-.472)2 + (0-.472)2) /3 = (.0378 + .0773 + .2228) / 3 = .113

  5. CVV Example (cont) • CVVj=.113, DFi,j={1,2,0} [from previous pages] • Given: query q has only one term in query: tj (M=1) • Gi,q = Sumk=1M(CVVk * DFi,k) = CVVj * DFi,jfor our example • G1..3,q = {.113, .226, 0} • So, collection c2 is “gooder” than the others... • Goodness is “only an indicator as to where, among the |C| collections, the query terms are concentrated at.” <-- bad grammar!

More Related