CS130 Software Tools. Fall 2010 Advanced Topics in Excel

Transcription

1 Software Tools Advanced Topics in Excel 1

2 More Excel Now that you are an expert on the basic Excel operations and functions, its time to move to the next level. This next level allows you to make your calculations more flexible and slightly smarter by using logical operations and specifically the 'IF' operator. Comparison Operators You can use comparison operators to compare two numbers, functions, formulas, or labels and return either true or false. Examples include: =2*3 =4+2 =A1>0 =average(a1:a10)>50 2

3 Conditional Excel Every conditional test must include at least one comparison operator. As an example, in the formula =A1>0, the comparison operator is >. The following six comparison operators exist in Excel Comparison Operators 3

4 IF a logical test Making a decision is essentially executing a test The Infamous 'IF' Function The IF function is very handy for detecting and indicating things about your dataset. As a function, it checks a condition that must be either true or false. If the condition is true, the function returns one value; if the condition is false, the function returns another value. The syntax of the IF function is: =IF(logical_test, value_if_true, value_if_false) What do we mean by a "logical_test"? Provide some examples of your own 4

5 Using Simple Formulas Examine the following spreadsheet that shows activity on a bank account. For type W the amount is withdrawn from the balance. For type D, the amount is added to the bank balance. What is the formula in cell D5 that could correctly be filled down to later transactions on the balance? 5

6 Logical Operators Sometimes our logical_test needs to use a logical function such as AND and OR. The syntax for each of these statements is: OR(logical_test#1, logical_test #2) AND(logical_test#1, logical_test #2) For the OR construct, a value of TRUE is returned if EITHER of the logical tests returns a value of TRUE; otherwise, a value of FALSE is returned to the cell. For the AND construct, a value of TRUE is returned if BOTH of the logical tests return a value of TRUE; otherwise, a value of FALSE is returned to the cell. Note that you can have more than TWO logical tests within an OR or AND statement by simply separating each subsequent logical test with a comma. Often, the OR and AND constructs are used within an IF statement. For example, the statement IF(AND(1<2,4=3),"HELLO","GOODBYE ) will return to the cell "GOODBYE" because both 1<2 and 4=3 are not true. However, the statement IF(AND(1<2,4=4),"HELLO","GOODBYE ) will return "HELLO" to the cell. 6

7 Nested IF Functions Remember the IF functions above? Well, you can create nested sets of IF functions. Recall that the syntax for IF functions is: =IF(logical_test, value_if_true, value_if_false) The (value_if_true) and (value_if_false) arguments can be: Values (numbers, strings, etc.) References (A1, B1, etc.) Functions (INT, SUM, IF) 7

8 Nested IF Functions When you use an IF as an argument in an IF function, then you have nested Ifs. =IF("if the condition stated here is true", then enter "this value, else if("if this condition stated here is true", then enter "this value, else enter"this value")) Example Automatically Assigning Grades =IF(A2>89,"A",IF(A2>79,"B",IF(A2>69,"C", IF(A2>59,"D","F")))) Look at all those Parentheses? Remember the result of all the IF statement goes in the cell where you have your function 8

9 Useful Functions NPER Financial Function Another useful financial function is NPER, which calculates the number of periods for an investment based on periodic, constant payment and a constant interest rate. This is how you can easily determined such things as your loan payment amount, or how long it will take you to payoff that new Impreza Sport It is a good starting place for rough calculations for such things as large capital investments for a business as well 9

10 NPER() 10

11 Useful Functions PMT Financial Function Calculates the payment for a loan based on constant payments and a constant interest rate. Syntax PMT(rate,nper,pv,fv,type) Where, rate is the interest rate for the loan. nper is the total number of payments for the loan. pv is the present value, or the total amount that a series of future payments is worth now; also known as the principal. fv is the future value, or a cash balance you want to attain after the last payment is made. If fv is omitted, it is assumed to be 0 (zero), that is, the future value of a loan is 0. Type is the number 0 (zero) or 1 and indicates when payments are due. Set type equal to 0 or omitted if payments are due at the end of the period Set type equal to 1 if payments are due at the beginning of the period The payment returned by PMT includes principal and interest but no taxes, reserve payments, or fees sometimes associated with loans. Make sure that you are consistent about the units you use for specifying rate and nper. If you make monthly payments on a four-year loan at an annual interest rate of 12 percent, use 12%/12 for rate and 4*12 for nper. If you make annual payments on the same loan, use 12 % for rate and 4 for nper. Tip: To find the total amount paid over the duration of the loan, multiply the returned PMT value by nper. 11

12 Excel Functions Excel has over 350 built-in functions divided into 10 categories, including financial, math, trig, statistical, text, logical, database, and information. There are really two different ways to enter functions into a cell: If you know the function well and the options for parameters, then probably just typing away is the best. Using the Paste Function dialog box. To invoke this dialog box, click on the fx icon (fx is short for function in mathematics) on the tool bar. 12

13 Excel Functions The easiest and best way to determine whether there is a function you can use and then how to use it is to use Help and then do a Search on Functions Be sure to read the description and to review the sample provided to make sure it does what you think it should 13

14 Goal Seek in Excel A What-If analysis is essentially the ability to change certain variables and they to see how the overall "model" changes. Goal seeking is a function under the what-if analysis tools. It is used when you know what answer you want in a cell and you want to get the other variables in the model to change to match the outcome desired. Remember we use the term model to mean how the real world question is represented in the tools, this is back to that idea about variables, time and your hypothesis. You could call all those elements a part of your model. Using Excel to scrutinize the impact of changing values in cells that are referenced by a formula in another cell is called what-if analysis. 14