Introduction to Engineering Computing GEEN 1300 Lecture 7 15 June 2010 Review for midterm

2 Double-click the Compute Re button. This will cause the following Sub wrapper to pop up in a code module: In here, we must add code to carry out the necessary calculations and display the Reynolds Number result Hooking VBA code to the “Compute Re” button…

3 This variable is the name you created for your textbox This is a variable you create and use in your calculation. Do NOT use the textbox name on the LHS of your calculation – it will not work!!

4 How to run and remove user forms insert a new module and add this Sub to start the UserForm double-click the Quit button and add the code to remove (“unload”) the UserForm run the StartReynoldsNumber macro… …and enter values with units selected

5 UserForms UserForms can be loaded automatically when the workbook is opened. (This is called an “event handler.”) And they can also be unloaded automatically when the workbook is closed. 1.Go to VBE and double click on thisworkbook item in Project Explorer. (If Project Explorer doesn’t show up, use view) 2. Change left field at top from General to Workbook. 3. Type in ReynoldsNumber.Show (this is not on any exam; it’s just a useful FYI)

6 Things to Remember!!! Create your own variables to carry out calculations, NOT the variables in the user form Make sure the variables from the user form that you assign to your created variables are the same names as in your user form These variables are those used from your text boxes and your option buttons, NOT your labels You should not have the same name for your text box as for your label

7 This variable is the name you created for your option button FormatNumber – number of digits after the decimal point. Does not round.

8 If you get a Reynolds number of and the program says MsgBox(FormatNumber(Re,1)), what will the message box say? a)2134 b)2135 c) d) e)2134.4

9 MsgBox Function MsgBox(“prompt”,buttons,”title”,helpfile,context) optional

10 MsgBox Function MsgBox(“prompt”,buttons,”title”,helpfile,context) optional Button codes vbOKOnlyvbExclamation vbOKCancelvbInformation vbAbortRetryIgnorevbDefaultButton1 vbYesNoCancelvbDefaultButton2 vbYesNovbDefaultButton3 vbRetryCancelvbDefaultButton4 vbCriticalvbSystemModal vbQuestion

11 MsgBox Function Putting line breaks into the message displayed: MsgBox result is button clicked by user

Announcements: Midterm exam Thursday at 8am Open book Open notes Open Excel/VBE No cheat sheet (duh) No collaboration

13 What the exam looks like: Excel: Displaying data (surface plots, creating xy grids) Fitting a model to a set of data points How good is the model overall? How good are the coefficients? Transforming equations to regression-friendly forms

14 What the exam looks like: VBE: Defining functions for use in spreadsheet Defining subs to manipulate spreadsheet Tracing through a function or sub (control flow) Calling a sub or function from another sub Fixing functions or subs with bugs Making a UserForm

15 How to study: Review all lecture notes Review all lab & homework problems Re-read any textbook sections & lecture notes that you need in order to fill in or clarify any shaky/fuzzy topics Think about Excel/VBA strengths & weaknesses and/or come to help hours with any questions

16 Excel syntax Precedence order, parentheses Cell references & cell addressing Formula copy How to translate equations & word statements to/from Excel Plotting Different types of models: Building them (see next slides) Evaluating them (R 2 & co.) Using them

17 Trendline & data regression What does each one do? What’s the difference between them? Which one do you use for what kind of problem? What do you feed into them and what do they return? How to transform equations so that these tools will work on them (also know when to do that and when you can’t) How to fit linear models if you don’t have these tools?

18 Excel, cont.: Goal Seek & Solver What does each one do? What’s the difference between them? Which one do you use for what kind of problem? What do you feed into them and what do they return?

19 Excel, cont.: Matrices Matrix math in Excel: naming, addition, subtraction, scaling, multiplication, inverse, determinant, transpose The identity matrix Systems of linear equations: How they correspond to matrix problems How to translate sets of linear equations to/from the equivalent matrix equation How to solve that matrix equation

20 Excel, cont.: Iteration How & when to use iteration Bisection What it does (including what a root is) How the algorithm works How to implement it in Excel

21 VBA: The environment VBA “world” & Excel “world” The VBE Modules: what they are & how you insert them The debugger: How you use it What it lets you find out How that’s different between Subs & Functions

22 VBA, cont.: Basic Syntax Write/evaluate VBA statements Know the basic functions (arithmetic, logic, relational) Understand the precedence rules Subs & Functions Know the differences Know how to write & use both

23 VBA, cont.: Decisions Know how to decode them and how to write them Including working with logical and relational operators Loops Know how all five loop structures work Be able to write one for a prescribed task Be able to figure out what a given loop will produce Flowcharts Be able to translate simple flowcharts to/from code

24 VBA, cont.: Modular programming Variables When, why, & how do you declare variables? When should you use different kinds of variables? Scoping Dialog boxes MsgBox & InputBox Understand them and use them User forms