Text Retrieval and Spreadsheets Class 4 LBSC 690 Information Technology

Agenda Questions Text and Document Retrieval Spreadsheets Database design

Document Retrieval Making documents is often easier than finding them! Browsing vs. Searching Lots of applications –Chasing down citations in papers you read –Web search engines –Managing your personal files Representations vs. Algorithms What makes a good query

Ways of Searching Documents Metadata Controlled vocabulary –Manual indexing based on named concepts Free text –Characterize documents by the words the contain Social filtering –Exchange and interpret personal ratings

“Exact Match” Retrieval Find all documents with some characteristic –Indexed as “Presidents -- United States” –Containing the words “Clinton” and “Peso” –Read by my boss In the simplest version, a set of documents is returned –Each is as likely to be useful as any other –Usually listed in date or alphabetical order

Ranked Retrieval Put most useful documents near top of a list –Put possibly useful documents lower in the list No need to exclude any documents –Just list those least likely to be useful last Two basic techniques –Similarity-based –Probability-based

Similarity-Based Retrieval Assume “most useful” = most similar to query Lots of clues to meaning –Repeated words are good cues to meaning –Rarely used words make searches more selective Easily combined –Compute a “weight” for each term –Add up the weights for query terms in a document

What’s a Spreadsheet? Large table containing numbers –May also contain labels to aid interpretation –Columns are named with LETTERS –Rows are named with NUMBERS –Cells are named like A4, C1,... Some cells are automatically calculated –Formula specified when spreadsheet is created –Values are recalculated continuously

How Spreadsheets are Used Record keeping (cassette tapes) Calculation (income tax) What-if analysis (cash flow) –Sensitivity analysis (exchange rate) Goal seeking (retirement planning) –Uses continuous recalculation (“iteration”)

How Spreadsheets are Used Record keeping (check book) Calculation (income tax) What-if analysis (cash flow) –Sensitivity analysis (exchange rate) Goal seeking (retirement planning) –Uses continuous recalculation (“iteration”)

More Spreadsheet Applications Library applications –Budget –Collection development –Shelving capacity Educational Applications –Grade records –Equipment inventory

Excel Demo Start Excel –Microsoft Office folder Open N:\SHARE\CLASS\POSTCARD.XLS –File menu Enter your 1999 (desired) income in cell B3 –Tax due is displayed in cell B4

Excel Demo Change the tax due –Place the cursor over B4 –Type “=B3*0.x” “=” tells Excel this is a formula “B3” refers to the number in cell B3 The “x” in “0.x” should reflect your political views –0.5 would take away half your money –Try different values in cell C3 What kind of spreadsheet use is this?

Excel Demo Add itemized deductions –Highlight row 4 (click on 4) –Select “Row” in “Insert” menu twice –Label A4 as “Deduction amount” –Label A5 as “Taxable income” –Put the appropriate formula in B5 –Change the formula in B6 as needed Note how it was copied from B4 with changes

Excel Demo Limit the deduction –Maximum of 50% of income or 10,000 Search for help on “maximum” Replace the formula in B5 with a more complicated one –You can use another cell to show a partial result