Hi Johann, To add to Noorain's explanation:
Boolean (True/False) values cannot be added, multiplied, averaged, etc. by aggregate functions such as SUM(), PRODUCT(), AVERAGE(), MEDIAN(), and SUMPRODUCT. In fact, boolean values are always completely ignored by aggregate functions. To summarize boolean values with an aggregate function, you must convert the the boolean to a number. When you use a value in a formula as if it were a different type of data, Excel will in most circumstances convert the value to that type of data. This implicit method of data type conversion is called coercion. You can coerce boolean values to a number, text representations of a number to a number, textual dates/times to actual date/times (dateserials), anything to text,. Boolean values can be coerced to a number (1 for True, 0 for False) in several ways. If you use an arithmetic operator with a boolean value, the boolean is coerced to become a number. In recent versions of Excel, the N() function performs an explicit conversion to a number and works in many circumstances (although arithmetic coercion works more broadly). For completeness there is also the similar VALUE function which can convert most data types to numbers, but not booleans. When you don't need to use an arithmetic operator in your formula already, but you need to coerce a boolean value, you have to device a neutral expression that includes an arithmetic operator, like --boolean, boolean*1, boolean+0, boolean/1. -- is often favored. Your formula is still clean, the -- form would probably not be used in other circumstances, and it's a fast calculation for Excel. Usually the requirement to utilize boolean values as numbers comes up in array formulas and SUMPRODUCT formulas (similar because SUMPRODUCT resolves array formulas too). Numeric representations of boolean values is useful in these formulas because when multiplied by another value, that value can either be included in a summary when the boolean is True/1, or not, when False/0. That boolean value or expression has become a criteria for what to summarize. Asa From: excel-macros@googlegroups.com [mailto:excel-macros@googlegroups.com] On Behalf Of NOORAIN ANSARI Sent: Wednesday, February 22, 2012 7:06 PM To: excel-macros@googlegroups.com Subject: Re: $$Excel-Macros$$ Meaning of minus minus or -- in an Excel function Dear johann, The -- is used as an unary operator to convert a boolean value ie, TRUE/FALSE in to 1/0. Sumproduct for example does not evaluate non-numeric values that results in a formula like the boolean results in the array equation A1:A10="johann". So to negate this, we use unary operator -- with TRUE or FALSE to give 1 or 0 We can also use ++ ,+0,*1 In fact you can also use a multiplier or a divisor of 1 In case you'd like more information, look up in google. Here's something from an Excel MVP http://www.mcgimpsey.com/excel/formulae/doubleneg.html On Thu, Feb 23, 2012 at 5:24 AM, johann <josle...@gmail.com> wrote: Hi Cyberspace, I'd like to understand the meaning of "--" in front of an Excel function like : =--sumproduct(...) =--substitute(...) ... and other I can't recall I know that in some programming language it's a way to "decrement" a variable like i = i - 1 can be i-- or --i following the precedence of the operator --. Thanks, Cyberuser -- FORUM RULES (986+ members already BANNED for violation) 1) Use concise, accurate thread titles. Poor thread titles, like Please Help, Urgent, Need Help, Formula Problem, Code Problem, and Need Advice will not get quick attention or may not be answered. 2) Don't post a question in the thread of another member. 3) Don't post questions regarding breaking or bypassing any security measure. 4) Acknowledge the responses you receive, good or bad. 5) Cross-promotion of, or links to, forums competitive to this forum in signatures are prohibited. NOTE : Don't ever post personal or confidential data in a workbook. Forum owners and members are not responsible for any loss. ---------------------------------------------------------------------------- -------------------------- To post to this group, send email to excel-macros@googlegroups.com -- Thanks & regards, Noorain Ansari http://noorainansari.com/ <http://excelmacroworld.blogspot.com/> http://excelmacroworld.blogspot.com/ -- FORUM RULES (986+ members already BANNED for violation) 1) Use concise, accurate thread titles. Poor thread titles, like Please Help, Urgent, Need Help, Formula Problem, Code Problem, and Need Advice will not get quick attention or may not be answered. 2) Don't post a question in the thread of another member. 3) Don't post questions regarding breaking or bypassing any security measure. 4) Acknowledge the responses you receive, good or bad. 5) Cross-promotion of, or links to, forums competitive to this forum in signatures are prohibited. NOTE : Don't ever post personal or confidential data in a workbook. Forum owners and members are not responsible for any loss. ---------------------------------------------------------------------------- -------------------------- To post to this group, send email to excel-macros@googlegroups.com -- FORUM RULES (986+ members already BANNED for violation) 1) Use concise, accurate thread titles. Poor thread titles, like Please Help, Urgent, Need Help, Formula Problem, Code Problem, and Need Advice will not get quick attention or may not be answered. 2) Don't post a question in the thread of another member. 3) Don't post questions regarding breaking or bypassing any security measure. 4) Acknowledge the responses you receive, good or bad. 5) Cross-promotion of, or links to, forums competitive to this forum in signatures are prohibited. NOTE : Don't ever post personal or confidential data in a workbook. Forum owners and members are not responsible for any loss. ------------------------------------------------------------------------------------------------------ To post to this group, send email to excel-macros@googlegroups.com
