Learn Ninja-Like Spreadsheet Skills with LESSON 9. Math, Step by Step

Transcription

1 EXCELL MASTERY Learn Ninja-Like Spreadsheet Skills with LESSON 9 Doing Math, Step by Step

2 It s Elementary, My Dear Ninja There is a scene in the short story The Crooked Man, where Sherlock Holmes accurately comments about how busy Dr. Watson has recently been. Watson, impressed by Holmes ability to know that, asks how Sherlock could have known. Sherlock says, I have the advantage of knowing your habits, my dear Watson. When your round is a short one you walk, and when it is a long one you use a hansom. As I perceive that your boots, although used, are by no means dirty, I cannot doubt that you are at present busy enough to justify the hansom. Excellent! says Watson. Elementary, corrects Sherlock. It wasn t that Sherlock Holmes performed any intense magic trick to raise his level of awareness. Nor did he have the superhero powers we talked about earlier. It was nothing extraordinary, just plain, simple, elementary logic. And an ability to string several elementary observations together to arrive at a profound result. That s what this lesson is about performing simple (elementary level) math functions in Excel. Then stringing them together to achieve profound results. Basic Math functions If you have never created a math function in Excel, this is your lucky day. Open the workbook, and go to the Basic tab. There are seven examples for basic math functions. In the white boxes on the right side, enter the formulas for each equation to the left. For example, in cell G6, type =C6+E6 and press Enter. You will likely breeze through the next four or five equations. In order, they should read: =C8-E8 =C10*E10 =C12/E12 =C14+E14-G14 Excel Mastery Page 2

3 SUM If Excel was a rock band, then the SUM function was their first big hit. It s what got them noticed, a record contract, and a ton of groupies. I know this because I was one of the groupies. Click on cell I16, and enter the following formula: =SUM(C16:G16) and press Enter. That s the way to sum a continuous range of cells. If, however, the cells are not cleanly presented to you in a single row or column, you can combine ranges by using a comma. For example, try entering this formula: =SUM(C6:E6,G8,C16:G16). It now includes numbers from the first two examples in its total. Order of Operations Excel follows the standard order of operations for calculating a formula. That means when you have any formula with multiple operators (add, subtract, multiply, divide), there is a consistent way to calculate the answer. Without a standard order of operations, x 5 could be either 20 or = 8, and 8 x 5 = 40 3 x 5 = 15, and = 20 The order of operations is this: Parentheses, Exponents, Multiplication, Division, Addition, Subtraction There s a very popular acronym to help you remember this order. It has nothing to do with anyone s dear aunt Sally. I mean, it make sense. Practice Excel Mastery Daily And Succeed!! So what does it mean? It means Excel will do anything inside parentheses first. Once it s done with calculating everything within parentheses, it then looks for exponents, and calculates them. Then multiplication, and so on until the formula is completely calculated. What does that mean for our formula above? 5 [addition] 3 [multiplication] 5 =?? Excel Mastery Page 3

4 There s addition and multiplication, and Multiplication comes first. 3 x 5 = 15. So we re left with Excel tells us it s 20. If we wanted the opposite result, then we would use parentheses to get us there. Since parentheses are always calculated first, it s a very useful tool for us. The formula would be: ( ) x 5 It s elementary. Enter a formula to calculate example 7. First without parentheses. Then with a set of parentheses around the first two cell references, and another set of parentheses around the second two cell references. Quite a difference! LOGIC The root of logic is cause and effect. If something, then something else. We re surrounded by logic and if-then statements in our lives. If I eat McDonald s five times a day, then I will gain weight. If I flip a light switch up, then a light turns on. Even Murphy s Law is a statement of logic. If something can go wrong, then it will go wrong. Transferring the ability to calculate if-then statements to Excel is like giving it the ability to think for itself. It s like adding an invisible employee to my team. I have Excel the intern at my disposal when I make effective use of logic statements. Only Excel doesn t call in sick. On the Excel workbook included with this lesson, go to the Logic tab. Example 1 has a random grade assigned to cell D6. In cell E6, we d like to make a formula that tells us whether the student passed or failed. The structure of an Excel IF statement is this: =IF(condition, do if true, do if false) For our purpose, the condition is to determine if the student s grade is below a passing score of 65. If it is below that number, then the cell should display the word Fail. If the statement is false (meaning the grade is 65 or higher), then the cell should display the word Pass. Here is the actual formula: =IF(D6<65,"Fail","Pass") Excel Mastery Page 4

5 Math is Lame NOT Example 2 requires that you use the NOT statement within an IF statement. In this scenario, a statement will be true if anything EXCEPT the case inside the NOT statement is true. Have you ever said I don t care what happens, as long as xyz doesn t happen? What you re saying, in Excel speak, is =NOT( xyz ). As long as it s not that one case, then all is well. For this example, a letter grade is assigned in cell D8. We want a formula in cell E8 to display Pass as long as the letter grade is NOT F. It can read pineapple for all we care. It just can NOT be F. Here s the formula: =IF(NOT(D8="F"),"Pass","Fail") OR OR is the next function. It s allowing for any one or more situations to be true, but it doesn t need all. Example 3 has the same letter grade as example 2. This time, however, we want a formula that looks for an actual passing grade in order for cell E10 to display Pass. Pineapple will no longer work here. Sorry, pineapple. Each statement you want checked within the OR function needs to be separated by a comma. Here s the OR function that checks for any passing grade: =IF(OR(D10="A",D10="B",D10="C",D10="D"),"Pass","Fail") AND Where the OR statement is looking for one of the several to be true, AND needs them all to be true in order to also be true. To illustrate how this would be used, example 4 has the number of completed lessons. For a student to graduate (and thus display graduate in cell E12), they must receive a passing grade AND have completed all 10 lessons. The conditions inside the AND function must also be separated by commas, just like how we did in the previous example. Here is the formula: =IF(AND(D6>=65,D12>=10),"Graduate","Repeat") If you were really observant, you noticed we used the equal to or greater than sign >= so if a student got exactly a grade of 65 or attended exactly 10 lessons, they will graduate. Excel Mastery Page 5

6 Nested IF Statement Have you seen the movie Inception? Where the characters have the ability to effect a dream while someone is already dreaming? It s a dream within a dream. That is the concept behind the Nested IF statement. It s an IF-THEN within another IF-THEN. Let s do an example. Example 5 shows the GPA of the student. If they pass, and if their GPA is 4.0, then the white box to the right should read Flying Colors. If they pass with any other GPA, then it should simply say Graduate. If they failed, then it should say Repeat. Start the formula like this: =IF(E6="Pass","Graduate","Repeat") We still need to test their GPA to determine if they passed with Flying Colors or not. So let s use a temporary cell. In E16, enter this formula: =IF(D14=4,"Flying Colors","Graduate") That formula will make sure the right words are displayed if the student passes. If they fail, it will still say "Graduate", and thatt is incorrect. So we will copy it and paste it into the original formula, replacing "Graduate". The finished product is this (in cell E14): =IF(E6="Pass",IF(D14=4,"Flying Colors","Graduate" "),"Repeat") The Nested IF! This is complex stuff, so don t be discouraged if you don t get it on the first try. Or the second try. Please me if you want more information on it: bobmaucher@gmail.com. Here s another way to see that formula Did they pass? Did they get 4.0? Flying Colors Graduate Repeat Excel Mastery Page 6

7 Statistics OK, take a deep breath. Nested IF statements are over with. It s smooth sailing from here on out. Click on the Statistics tab, and let s get started. MIN & MAX The MIN function finds the lowest value in a range of numbers that you define. The MAX function, well, yes, you probably already guessed that it finds the largest value in a range of numbers. Let s see them in practice. Example 1 asks for the minimum value in a range of cells (16 numbers) to the right. Enter this formula into cell D6: =MIN(F6:I12) and press Enter. The result is the lowest number out of the 16 values in the box at the right. The MAX function is almost the same. Just replace MIN with MAX, and use the same range. You now have the largest number in that range. AVERAGE & COUNTA This is just as easy as the last two functions. Cells with no values in them (blank cells) are not factored into the average. If, however, there is a value of 0 in the cell, then it will be counted in the overall average. So in D10, enter this formula: =AVERAGE(F6:I12) and press Enter. Then, in cell D12, enter this: =COUNTA(F6:I12) and press Enter. So you now have the average of all values in the range to the right, as well as the count. The count should be 16 and not change, as there are 16 numbers in that range. There is also a function called COUNT, which only counts numerical values. It won t make a difference here, but if you are trying to count cells which have text values included, only use COUNTA. RANK This function tells you in which place a given number falls. For example, if the data set is 1, 2, 4, 6, 8, 9, the number 6 has a RANK of 3, as it is the third highest number. In example 5, you re asked to find the RANK of the value in cell F14. The formula should look like this: =RANK(F14,F6:I12) Excel Mastery Page 7

8 Cool Math Tricks Finally, there are some miscellaneous great tools that I use regularly for fun and profit. To follow along, head to the Tricks tab in the workbook. And here they are. IFERROR Don t you hate it when a nice looking spreadsheet is ruined by #DIV/0 errors? And his cousins, #N/A and #REF! Well fret no more! IFERROR checks the equation first to see if it will result in an error. If it does, then it replaces it with any value that you set. If it doesn t have an error, then it proceeds to calculate as normal. In cell G6, type this: =IFERROR(C6/E6,0) That says to divide C6 by E6. And if it results in an error (like if E6 = 0), then replace the error with a 0. Neat! ABS Absolute values. Which means they re always positive. Negative numbers are turned into positive ones, with the same value. Replace the formula in cell G8 with this one: No more negatives! =ABS(C8-E8) ROUND The ROUND function will adjust a value according to the criteria you set in this formula. You can make it so that it rounds to the nearest integer, or the nearest tenth, hundredth, and so on. Round the formula in G10 to the nearest integer by using this formula: =ROUND(C10/E10,0) The 0 means we want no decimal places. If you had a 1 instead, it would round to the nearest tenth. RANDBETWEEN I used this function throughout the examples. It s a great way to come up with numbers when you want to randomize things. This will output a random integer, between two numbers that you set. Want a random value between 1 and 1,000? =RANDBETWEEN(1,1000) For example five, write a formula to produce a random number between any two numbers shown in cells C12 and E12. Excel Mastery Page 8

9 ROMAN This one is really cool. It converts any number to Roman numerals. The formula layout is =ROMAN(cell reference). Figure out the current year s Roman numeral representation by using this function in cell G14. The Step by Step Method In closing, I d like to go back to our Nested IF lesson, and revisit how we got to our solution. The process of calculating one part of a complex formula at a time is so important to developing advanced functions. I have engineered formulas that ran over three lines in the formula bar. But there s no way I, nor anyone else could come up with a formula like that on the fly. I created a little piece of formula in one cell, then another piece in the cell next to it. I continued until all pieces were calculating correctly. Only then would I piece them together in a single formula. Tips to mastering the Step by Step Method of Building Super Crazy Long Formulas: 1. Know your end goal when you start. If it s to total a bunch of different numbers, then know that. If it s to display a string of text, then keep that in mind as you craft the formula 2. Use hard-coded sample numbers to help get a picture of what the formula should do. 3. Write your formula in English logic IF the cost is less than $50,000 then check the location, and if it s in Charlotte, then assign a spreadsheet ninja. 4. Draw! Sometimes putting pen to paper helps visualize what you need to calculate next. 5. Be Patient. Sometimes these formulas take a while to build. If you find yourself getting stuck, then walk away and take a break. Come back later with a fresh set of eyes. I can t wait to see what you come up with! Excel Mastery Page 9

10 Reference Basic Math + - * / SUM add a range, separate ranges with commas Remember the order of operations P.E.M.D.A.S. When in doubt, use parentheses to ensure the correct order Logic IF cause / effect =IF(statement, do if true, do if false) NOT reverses the truth, you re looking to disprove OR any one of several conditions may be true, separate with commas AND all of several conditions must be true, separate with commas Nested IF Multiple decisions checked in one formula, build one at a time, then combine Statistics MIN smallest number in a range MAX largest number in a range AVERAGE average value of all numbers in a range COUNTA the number of values in a range (including text values) RANK the place of a number, from largest by default Cool Math Tricks IFERROR replaces error messages with any value you set ABS absolute values get rid of negative numbers ROUND round a decimal to the nearest integer (or tenth, hundredth,, ) RANDBETWEEN output a random integer between two values you set ROMAN convert a number to roman numerals The Step by Step Method Know your end goal Hard-code sample numbers Use English logic Draw it out Be Patient Excel Mastery Page 10