formula

Error Trapping in Excel

Geeks Computer Tech - 02.41

I had a query about how to set up a spreadsheet for future rows to be added but without showing all the error messages you get when a formula expects there to be something in a cell which hasn't yet had data entered. <a href="http://4.bp.blogspot.com/_i9xWjDR4D-E/TH4gT5-UQQI/AAAAAAAAGDA/5zrhPqp0_5A/s1600/20100901a.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5511878520299864322" src="http://4.bp.blogspot.com/_i9xWjDR4D-E/TH4gT5-UQQI/AAAAAAAAGDA/5zrhPqp0_5A/s400/20100901a.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 334px;" /></a>Here's an example spreadsheet that works out how many miles per gallon of fuel you are using. I'm old enough to not want to know how many miles per litre I am getting so the spreadsheet converts the litres I buy into gallons. I have entered data up to row 8 but from row 9 downwards there are either errors or data showing where I don't want to see anything until data is entered into those rows. The only data I need to enter will go in column A (the date I buy fuel), column B (the mileage shown on the odometer of my car when I refuel) and column D (the number of litres I put in the tank). A formula in cell C9 =B9-B8 calculates how many miles since the last refuelling. Because there is no data in cell B9 it has calculated a value of -4328 ie zero minus the value in cell B8. <a href="http://3.bp.blogspot.com/_i9xWjDR4D-E/TH4jTMFKW1I/AAAAAAAAGDI/1RwsJs80DX0/s1600/20100901b.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5511881806515428178" src="http://3.bp.blogspot.com/_i9xWjDR4D-E/TH4jTMFKW1I/AAAAAAAAGDI/1RwsJs80DX0/s400/20100901b.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 334px;" /></a>The display in cell E9 is even worse because there is an error message displayed due to the lack of data in cell D9 which is causing a Divide by Zero error. The formula in cell D9 is =C9/(D9/4.546). The bit inside the brackets (D9/4.546) converts the number of litres into gallons. Then the number of miles travelled, held in cell C9, is divided by the number of gallons to give the miles per gallon figure. There really is no error here in human terms because the data simply hasn't been entered yet. But unless we want to copy the formulae down every time we add a row of data, the spreadsheet will see a logical error and report it. So we can use a simple =IF formula to test for the existence of a value in the critical cells before displaying anything. <a href="http://2.bp.blogspot.com/_i9xWjDR4D-E/TH4o8C8RjsI/AAAAAAAAGDo/KSG-3S1rh1c/s1600/20100901c.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5511888005995007682" src="http://2.bp.blogspot.com/_i9xWjDR4D-E/TH4o8C8RjsI/AAAAAAAAGDo/KSG-3S1rh1c/s400/20100901c.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 334px;" /></a>In cell C9 we have the formula =IF(B9="","",B9-B8). Let's break down the =IF syntax first then look at what it is doing. It uses the commas to separate the different segments and takes the form =IF(you find this, then do this, otherwise do this) If a cell contains nothing, that can be represented by placing the contents (nothing) between a set of double quote marks - "". Note that there is a big difference between nothing and a zero! So we can't use =IF(B9=0... So the formula is saying; =IF(B9 holds nothing, do nothing, otherwise display B9-B8) <a href="http://1.bp.blogspot.com/_i9xWjDR4D-E/TH4m4FhUGkI/AAAAAAAAGDY/tpL7kygfK4s/s1600/20100901d.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5511885738944502338" src="http://1.bp.blogspot.com/_i9xWjDR4D-E/TH4m4FhUGkI/AAAAAAAAGDY/tpL7kygfK4s/s400/20100901d.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 334px;" /></a>Likewise we can add a similar =IF to the formula in cell E9, in which case the existence of a value in cell D9 are the key to whether we want a value displayed or not. =IF(D9="","",C9/(D9/4.546)) The formulae can be copied down both columns B and E and each time you refuel you just need to add data to columns A, B and D to complete the row.

02.41

Excel: Manipulating text with LEFT, RIGHT, LEN, FIND, IFERROR

Geeks Computer Tech - 02.56

This entry solves the problem of having a single field for someone's name in a spreadsheet but then wanting to split it into forename and surname - perhaps because you want to sort rows alphabetically by name - hmm... yes... there's another entry to come! This one was suggested by a colleague, Patrick Bellis and he did actually provide a solution as well. I've had a fiddle and come up with an enhanced version though that shows how to deal with entries that have two forenames or a middle name or initial. It doesn't deal with more than one middle name or initial although you can do that easily - details later! <a href="http://1.bp.blogspot.com/_i9xWjDR4D-E/SmbkrfRzgDI/AAAAAAAAE4o/G3d1q5EEQNE/s1600-h/20090722a.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5361223842212839474" src="http://1.bp.blogspot.com/_i9xWjDR4D-E/SmbkrfRzgDI/AAAAAAAAE4o/G3d1q5EEQNE/s400/20090722a.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 228px;" /></a>So in my simple example, the Full Name field was the previously existing field and I have used formulae to split this into the two new fields, Forename and Surname. Now I have to say that this isn't my preferred way of doing this. My preferred way would be to use a Visual Basic (or VB) routine in a macro, but whilst these work for me quite easily in MS Access - the database application that comes with Microsoft Office Professional, I've never managed to get VB macros to work in Excel even when my efforts look exactly like the example in the Help pages. Someone else will have to suggest a fix for that perhaps? The VB routine would allow me to search for the last space within the name field. Using a simple formula, we have to search for the first space and that's why there's a problem with people who have middle names. To get over this partly - more specifically to deal with people who have a single middle name or initial - I've used a third new column which I've placed over to the right, out of the way where it doesn't need to be seen or printed. It's doing nothing other than an interim calculation or manipulation of the Full Name field. <a href="http://4.bp.blogspot.com/_i9xWjDR4D-E/Smblu2MAnRI/AAAAAAAAE4w/SeKFO6sZFQ4/s1600-h/20090722b.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5361224999413783826" src="http://4.bp.blogspot.com/_i9xWjDR4D-E/Smblu2MAnRI/AAAAAAAAE4w/SeKFO6sZFQ4/s400/20090722b.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 224px;" /></a>I've left a blank column between the working bits of the spreadsheet and this interim field but in reality you may want to hide it away far over to the right - say in column Z or even ZZ! This interim field searches for the first space and will contain all the text that comes after that first space. But before we look at the formula for that field let's deal with the simplest formula - that for the Forename field. Before we even do that let's look at the common syntax (the use of characters and the order they must be used) that formulas in Excel have. Any formula starts with an equals sign (=). This tells Excel that we want it to calculate something rather than treat the following characters as a string of text. Many formulas use brackets (or parentheses to give them their posh name) to contain any parameters the formula needs to work and use commas (,) to separate each parameter. The formula name tells Excel what to do and the parameters tell it what to do it to and how. A bit like: =DO-THIS(Do it to this, Do it like this) Formulas can be nested. That means we can use one formula to calculate the parameters for another formula. To find the Forename from the Full Name we need a formula that does this: RETURN THE CHARACTERS(from the Full Name, until you reach a space) For the Forename in Row 3 (so in the cell C3) the formula is: =IFERROR(LEFT(A3,FIND(" ",A3,1)),"") There are three different functions here and as with all mathematical formulae you should start by understanding the innermost set of brackets first. That set contains the parameters for the FIND keyword. The FIND formula counts the character that contains the first character of the string we want to find (the example will make this clear). The syntax for FIND is: FIND(the string of text you want to find, the string of text you want to find it within, the first character within the original string that you want to start searching from) Whoa! Too Much! Don't panic yet - I'm about to explain step by step. Step 1. The string of text we want to find is a space. So in the actual formula a few lines up you see ...FIND(" "... Step 2. The string of text we want to find the space within, is the Full Name field. So instead of actual text we have a pointer to cell A3. So far we have explained ...FIND(" ",A3... Step 3. I've put a figure one - 1 - because I want to start searching from the first character. Now; you could argue that there shouldn't be a space until at least the second character so I should have used a 2. But whilst there shouldn't that doesn't mean there won't be a space as the first character. Someone might have wanted to put their first initial and then their surname but not pressed the initial key hard enough. So by using a 1 instead of a 2, we do a simple bit of error trapping. So that should explain ...FIND(" ",A3,1)... The result of that bit of the formula is the number of the character that contains the space as counted from the left. So as cell A3 contains the text "John Burke" the FIND formula should find the space in character 5 and that is the "result" or "return" of the FIND formula. In the next cell down when considering the string "Seamus O'Leary", the space is the 7th character so the FIND formula returns 7. Thus as we consider the next most inner bit of the formula - which is the LEFT keyword - I can simplify the formula for you. Instead of considering: LEFT(A3,FIND(" ",A3,1)) we can consider it as: LEFT(A3,5) because Excel calculates the innermost formula first and works outwards, so once the FIND formula has run the LEFT formula works using the result. The LEFT formula chops and returns the text from the start (left) of the target string depending on how many characters you want. The syntax for LEFT is: LEFT(a string of text, the number of characters starting at the left of the string that we want to use) Again the string of text we want to use is contained in cell A3 so we have LEFT(A3... and the number of characters we want to use (as calculated by the FIND formula) is 5. So LEFT(A3,5) is the same as LEFT("John Burke",5) and the result is "John ". Note that there is a space at the end, because we asked for 5 characters. It won't show so it doesn't matter, but if you wanted to be pedantic (anyone having problems with the formula should ignore this as over complicated) we could have used LEFT(A3,FIND(" ",A3,1)-1) which would have subtracted 1 from the value returned by the FIND. Ahem! But that's just being a clever clogs! So that just leaves us with the IFERROR bit of the formula and what that does is it stops Excel from coming up with an error message if there is no space at all. Basically the syntax for IFERROR is: IFERROR(I want Excel to do this, but if it finds an error then do this instead) In the last parameter I've used two double quote marks "" - or in other words I've told Excel that if there is an error, instead of reporting that there's been an error it can show the text within the quote marks. Which is nothing. No text at all. The cell would be empty. Excel isn't good at telling you what's wrong; it just tells you there has been an error. <a href="http://1.bp.blogspot.com/_i9xWjDR4D-E/Smb3qhqi_SI/AAAAAAAAE44/nqQ-Ewbv7u8/s1600-h/20090722c.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5361244716394544418" src="http://1.bp.blogspot.com/_i9xWjDR4D-E/Smb3qhqi_SI/AAAAAAAAE44/nqQ-Ewbv7u8/s400/20090722c.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 217px;" /></a>Without the IFERROR formula if there is no space at all then you just get the dreaded #VALUE! error, which tells you absolutely nothing! See Row 7 in the screen grab. And so to the surname... Unfortunately there is no way of saying 'Now take the rest' after having done a LEFT formula. But there is a RIGHT formula which does the same as the LEFT only from the rear of the text string. RIGHT(a string of text, the number of characters starting at the right of the string that we want to use) Our problem now is that just because we know the position of the space, that still doesn't tell us how many characters we want from the right hand end of the Full Name, because we don't know how many characters there are in the surname. So we need to know how long the entire string of text is and to do that we use the LEN formula: LEN(a string of text) The LEN formula only needs a single parameter and returns a number which is the number of characters contained within the string. LEN("Fred Bloggs") would return 11. (it's counting the space as a character don't forget) LEN(A3) returns 10 - because cell A3 contains the text "John Burke" What we need for the Surname is the length of the Full Name minus the length of the Forename. So including our error trap use of IFERROR in case there is no space character, our formula is: =IFERROR(RIGHT(A3,LEN(A3)-FIND(" ",A3,1)),A3) Break it down from the innermost formula(s) in the nest. That's LEN and FIND. Both return numbers and we are taking LEN formula and then subtracting the result of the FIND formula. That gives us the number of characters to be returned by the RIGHT formula and as long as there is a space existing in cell A3 then we have our final result. The IFERROR formula this time, instead of returning no text at all, returns all of the Full Name field - assuming that any text with no spaces will be a surname. You can change this round if you keep a spreadsheet of celeb names such as Madonna or Prince! IFERROR(the main formula,A3) Now I just need to explain the interim field. The nested formula for the Surname as described above would take everything from the first space. So if there is a middle name or initial then you get that plus the Surname. I've created an interim field with the formula just described and then the Surname field has a formula that is exactly the same but which takes its original text string from the interim field instead of the Full Name field. You could have as many interim fields as you want, each whittling a middle name or initial out of the final surname, and with no errors even if there is no middle name. 12 such interim columns would let you deal with those unfortunate people whose father named them after the long-forgotten football team in the 1960s or 1970s!

02.56

Excel - Counting Occurrence of Text Values

Geeks Computer Tech - 06.12

Here's a poser I was asked today. Someone had an existing spreadsheet that had a column containing text, but she wanted a count of the occurrence of certain values. Let's look at a simple example of what she wanted. <a href="http://4.bp.blogspot.com/_i9xWjDR4D-E/SYBotwpmFnI/AAAAAAAAD_k/vkg0aXO9mt0/s1600-h/20090128a.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5296348297150469746" src="http://4.bp.blogspot.com/_i9xWjDR4D-E/SYBotwpmFnI/AAAAAAAAD_k/vkg0aXO9mt0/s400/20090128a.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 253px;" /></a>A summary of how many fields contain "red", how many "blue" and how many "yellow" is required. Now I'm going to keep this simple but if it was possible to enter either "red" or "RED" or "Red" or, worse, "scarlet" then the solution would be a bit more complicated, though still possible - perhaps a future entry to come! Here though the users have been told to use just the standard term, using lower case throughout. So the field only contains one of three possible values with a fourth value perhaps being an empty field. Here's a simple solution. There are other solutions more complicated but more elegant in that they don't require the use of any extra cells in the spreadsheet. Again perhaps a future entry will look at these (there's more than one way to skin this particular cat as there are in most forms of computing!) <a href="http://3.bp.blogspot.com/_i9xWjDR4D-E/SYBpk5qtyeI/AAAAAAAAD_s/qDvUMzJJsNw/s1600-h/20090128b.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5296349244463892962" src="http://3.bp.blogspot.com/_i9xWjDR4D-E/SYBpk5qtyeI/AAAAAAAAD_s/qDvUMzJJsNw/s400/20090128b.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 253px;" /></a>I've used the next three columns to calculate a numerical value registering the instances of each colour - a column being required for each of the three colours. In other words, I've not entered all those zeros and ones, the spreadsheet has used a formula to determine what value should be in each cell. The solution uses the if statement which follows this syntax form =if(argument being tested, value if true, value if false) The equals sign ( = ) is necessary before the if so that Excel recognises that what follows is a formula and not a piece of text. The argument being tested here is does the value of cell A2 equal the text within the quotes - ie red? It does so the argument is true, therefore the value if true part of the formula is used which in this case is a numerical 1. Note that if we had wanted a text value we could have used quotes and text messagea as the value if true and value if false e.g.: =if(A2="red","A red lover!", "What's wrong with red?") I needed to type in the formula for the first row only. After that I selected those three cells and used the <a href="http://computerbasicsforfree.blogspot.com/2008/11/click-and-drag.html">click and drag</a> technique to copy them down the columns. Excel is clever enough to know that if you copy in this way it will amend the formula for each row to calculate from that row - instead of every row calculating using the value in the first row. All we need to do now is add up each column for our summary. We could put a count at the bottom of each column and then use that or we could use the sum formula like this: <a href="http://4.bp.blogspot.com/_i9xWjDR4D-E/SYBtRB-F9WI/AAAAAAAAD_0/aCgiYV1bsd4/s1600-h/20090128c.jpg"><img alt="" border="0" id="BLOGGER_PHOTO_ID_5296353301141779810" src="http://4.bp.blogspot.com/_i9xWjDR4D-E/SYBtRB-F9WI/AAAAAAAAD_0/aCgiYV1bsd4/s400/20090128c.jpg" style="display:block; margin:0px auto 10px; text-align:center;cursor:pointer; cursor:hand;width: 400px; height: 379px;" /></a>And the job's a good 'un!

06.12

Geeks Computer Tech

Error Trapping in Excel

Excel: Manipulating text with LEFT, RIGHT, LEN, FIND, IFERROR

Excel - Counting Occurrence of Text Values

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