©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 1 Module Standard/Generic Applications Software for Modelling Data

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 2 Characteristics of Modelling Software  Characteristics of modelling software Ability to enter text, numbers and formulae in a cell Can create graphs based on the data Recalculation of answers based on changed values (‘what-if?’) Complex rules and functions to make decisions  Types of Modelling Software Spreadsheets – Excel, Lotus 1-2-3, Quattro Virtual Reality modelling software: VRML »Weather forecasting »Garden/Kitchen Design, etc

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 3 Variables and Formulae  Variables An identifier associated with a value stored in the model. The value may be in a cell or in memory  Formulae Formulae allow calculations to be represented in a spreadsheet. As well as numbers, a formula uses the addresses of cells to identify other values to be used. The result is placed in the cell in which the formula was placed If any of the cells used on the formula change their value, the result of the formula is updated »E.g (I2-2*B3)/2

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 4 Functions and Rules  These are special types of formulae used in a spreadsheet  They are used to represent formulae that may be too large or complex for the ordinary user to enter: SUM() – to add a range of numbers AVERAGE() – to calculate and average of a range HLOOKUP() – to find one value based on another IF() – to make a decision based on a value

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 5 ‘What-If?’ Questions  Answering ‘what-if?’ questions A model can recalculate values – this allows single values to be changed and the rest of the model to be updated automatically Various combinations can be tried with minimal effort What if questions are predictive by nature  Benefit of using a data model for ‘What if?’ questions: Only one model needs to be created and then altered Many different possibilities can be tried - repeatability Mistakes can be eradicated prior to construction Cost of creating a changeable model against several different models Safety of the model – nuclear explosion, trip to Mars Control over the variables

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 6 Worksheets, Rows, Columns, Cells and Ranges  Worksheets and Workbooks A number of worksheets within a single file is called a workbook. A workbook can be used to divide information between different sheets, for example income on one sheet, expenditure on another, and a summary on a third  Rows Rows are a horizontal group of cells. In Excel they are identified by Number  Columns Columns are a vertical groups of cells. In Excel they are identified by Letter  Cells A cell is the square on a spreadsheet in which only a single entry can be placed. The entry can be text, numbers or a formula. It can be referred to by its address based on its row and column  Ranges A range is a group of cells – usually identified by the address of the top left cell to the bottom right cell: A1:G5 for example

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 7 Absolute and Relative Replication  Replication is the process of copying a formula from one cell to another As a formula usually involves references to cells, it is necessary to know whether you want to keep the references the same (absolute reference) or change according to the row or column movement (relative reference)  An absolute reference always refers to the same cell  A relative reference changes the cell it references according to the movement of the target cell

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 8 Examples of Cell Replication The formula in Cells C2:C4 are replicated using both relative and absolute replication. When the cell is replicated down, the reference to B2 needs to change so that the price changes. ABCD 1GoodPriceVAT PayableVAT 2Pen£50=B2*$D$217.5% 3Watch£200=B3*$D$2 4Ring£500=B4*$D$2 However, the reference to cell D2 cannot change. If it was to change to cell D3 the formula would not work, as there is nothing in cell D3. Therefore as C2 is replicated, the reference to B2 needs to change, hence it is a relative reference, but the reference to D2 must not change, so it is absolute.

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 9 Graphical Representation of Data  Various types of Graphs: Column, Bar, Pie, Line, Area, Radar, Scatter, Surface, Bubble, Stock, etc  Uses of Graphs Pie Chart »A pie graph allows us to compare parts of the whole with each other, or the fraction of the whole each part takes up Line Chart »A line graph is a good way to look at how something changes, usually over time or sometimes across space Column/Bar Chart »Bar graphs are great for looking at differences amongst similar things. If we wished to know the number of marine mammals sighted, a bar chart could be used to show which marine animals are the least and most seen, out on the water

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 10 Customisation of Spreadsheets  Form Controls These include items such as: »Spinners »Drop down boxes »Buttons They are used to increase the usability of the spreadsheet – list/drop down boxes can limit data entry, making validation easier for example Buttons can run Macros

©G. Millbery 2000Standard/Generic Applications Software for Modelling DataSlide 11 Customisation of Spreadsheets (Cont)  Macros A sequence of instructions defined as a single element A macro has an identifier – usually a single word which can be used to call the macro Macros add a degree of programmability to the application A Macro is an easy way to allow novice users to run complex instructions by the use of a single command »This could be commands such as formatting text, creating graphs, analysing data or even moving from one part of the spreadsheet to another