Excel: What-if Analysis. Tutor: Pan Hong Date: Sep 8, 2016

Transcription

1 Excel: What-if Analysis Tutor: Pan Hong Date: Sep 8, 2016

2 Basic Data Analysis Sorting Filtering Subtotal Table Pivot Table

3 Advanced Analysis Data Table 模拟运算表 What-if Analysis Scenarios 方案 Goal Seeking 单变量求解 Solver 规划求解 Add-Ins Analysis ToolPak 分析工具库 Statistics

4 What-if Analysis Sensitivity Analysis Decision Making Constructed Mathematical Model Outcome Evaluation Influential Factors Function Relation y = f (x1, x2, )

5 Single-Variable Data Table (1) Create Step1. Create a List (values for substitution) Step2. Interested outcome declaration Formula definition Step3. Range selection (including the list) Data -> What-if Analysis -> Data Table Row / Column Input Cell: the single variable The cell substituted with varying values

6 Single-Variable Data Table (2) Clear or Delete Horizontal Data Table Multi-formula Table Format Number: concurrency Field name defining: readability Table refresh Input cell modified: automatic calculation Cells inside: non-revisable

7 Double-Variable Data Table Two influencing factors Create Row input cell Column input cell Note: only one destination cell Table Refresh: formula modified Used to solve equation Row input cell and column input cell defined as two dependent variables Row list and column list include the possible values Outcome formula refers double-variable

8 Feature of Data Table Contrast with General Method (range) Define formula and then copy Data Table Data as a whole part Formula defined uniformly Unable to modify single cell in particular No need to consider absolute or relative reference Arguments in formula: column or row input cell reference

9 Scenarios Different with Data Table more than two influential factors Under Particular Circumstances Combination of all arguments with special values

10 Scenario Usage (1) Data -> What-if Analysis -> Scenario Manager Formulas -> Defined Names: Create from Selection: left column (optional) Create Scenario Manager -> Add Name Changing cells Press Ctrl for non-adjacent cells selection, less than 32 Comment Creator name and date by default Protection Enter Values Note: worksheet based

11 Scenarios Usage (2) Modify Scenario Manager -> Edit Delete Merge Import Scenarios from other workbook or worksheet Display Scenario Manager -> Show Volatile source data

12 Scenarios Usage (3) Generate Scenarios Report Scenario Manager -> Summary Report type Scenario summary Scenario Pivot Table report Result cells Recommendation by default Press Ctrl for non-adjacent cells selection

13 Comparison Similarity Perform value substitution to evaluate the outcome changes Difference Data Table: Assign a value sequence to one or two independent variables Scenarios: Assign an individual value to a series of independent variables

14 Reverse What-if Analysis Desired result fixed, to find conditions on influential factors Goal seeking: single variable y = f(x) Solver: more than one variable y = f(x 1,x 2, )

15 Goal Seeking Desired result from a single formula known, to find the determined input value Function relation y = f(x) x = f -1 (y) f -1 :inverse function Excel: adjusts the value in one specific cell until the dependent formula reaches the result Note Solution: possibly no existence Configuration File -> options -> Formulas -> Calculation: maximum iterations

16 Goal Seeking Usage On Worksheet Data Data -> What-if Analysis -> Goal Seek Set cell To value By changing cell On Chart (Only for Version_2003) Data Point selection: destination Drag and drop Equation Solving Blank cell: independent variable naming x (Note: Scope) Formula input Goal seeking: destination value to 0

17 Solver Optimization: find the best way to do something Mathematically: max/min f(x 1,x 2, ) In excel Find the values of certain cells in a spreadsheet that optimize a certain objective Not launched by default Install: File ->Options -> Add-Ins -> Manage Excel Addins -> Go: Solver Add-In Use: Data -> solver

18 Create Model Target cell Objective Maximum profit Minimum cost Changing cells Decision variables: value adjusting Function relation with target cell Constraints Restriction placed on changing cells Represented with equations or in-equations

19 Example A company need to buy 4 kinds of gifts, with different unit prices, to do promotion. Quantity of each kind of gift must reach some requirements. Try to minimize the total cost. Model Variables: x 1,x 2,x 3,x 4 Conditions x 1 400, x 2 600, x 3 800, 200 x x 1 + x 2 + x 3 + x 4 = 4000 Goal Min(c 1 *x 1 +c 2 *x 2 +c 3 *x 3 +c 4 *x 4 )

20 Solver Usage Data in a table Solver parameters Set Target Cell Equal To By Changing Cells Subject to Constraints Add Solve Solver Results Save Scenario Reports Selection Answer Sensitivity Limits

21 Solution Analysis Solver Report Solver Parameters Configuration: Solver Options Max Time Running Iterations Tolerance Precision Convergence

22 Note Existence of Answer Feasible Solution Optimal Solution Limits Optimal? Initial values of decision variables on non-linear programming deeply impact the final result Professional solver Frontline Systems, Inc Upgrade the Excel Solver

23 Thanks!