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Introduction to Data Management Lecture 2 1 Overview • A little history • Other computer-based spreadsheet systems • What is a spreadsheet? • Types of Data • KDD Process Spreadsheet Beginnings • Pencil and Paper • ’78 Dan Bricklin – Harvard Business School – Use time sharing mainframe or pencil & paper (and eraser too probably) for large project – Neither were viable choices • Created VisiCalc for PC of the day – Apple II Spreadsheet Beginnings • In the beginning, VisiCalc could handle 5 rows x 20 columns – not extremely useful. • Made more robust by Bob Frankston and became a huge success • Michael Kapor developed Lotus 1-2-3 in early 80s – Lotus was the first app to begin the ubiquitous inclusion of computers in the business enviro. Spreadsheet Beginnings • Then enters Microsoft with Excel in ’84. – Started out written for Apple Macintosh because of windowing ability – Moved to DOS (’87) and then to Windows (’89) – Remained the flagship windows product for 3 years • Little competition until 1992 First Spreadsheet Program http://www.bricklin.com/ Other Spreadsheets http://www.gnome.org/projects/gnumeric/ Lotus 1-2-3 (older Windows ver.) Open Office Calc Excel 2003 What is a Spreadsheet • Rows and columns intersecting in cells? • Allows a 2D spatial relationship to be imposed on data =c1r1*c2r1 C1 R1 R2 C2 C3 1.1 2.2 2.42 4.4 3.3 14.52 =c1r2*c2r2 What is a spreadsheet? • Pieces of data and…. • Formulas to look at the data in a particular way. – Where information comes from – Power lies in the ability to use complex formulas. Value Recalculation • When a cell for which a calculated value depends is changed, the calculated value is automatically updated. • How???? – Is the value of every cell in the whole spreadsheet re-calculated? Types of Data • Different types of data require different reactions to operators – August 24, 2005 – 4 = ? – August 24, 2005 – 25 = ? • Some operators don’t operate on some types of data – Addition and string data Types of Data • • • • Textual Numeric Dates Calculated values – Contains references (absolute or relative) to other cells in spreadsheet, workbook, etc. KDD • Knowledge Discovery in Data (KDD) – Finding useful, possibly hidden, information in data Initial Set of Data Data Required Preprocessed Data Transformation Knowledge/ Information Model Transformed Data KDD Process • Selection – Finding the data that you want to analyze • Preprocessing – Erroneous data removed – Missing data supplied or predicted • Transformation – “Massage” data in to most usable form KDD Process • Data Mining – Apply data mining algorithms – Discovery • Interpretation/Evaluation – Interpret what you’ve discovered – Put in usable form – Visualization techniques