On 11/06/11 11:29, Tom Davies wrote: > Hi :) > > Regina, this is not a criticism of you but just some of my anger at the world > that gave me a fairly decent education in sciences and maths and made me > practically unemployable as a result. > > > Ok, again > > -3 x -3 = 9 > > I think people tend to expect the - to make the result -9. Perhaps they > expect > the result to be the same as -(3^2) which is a completely different thing. > Again this is more about people lack of maths understanding than about > spreadsheets. An evening course or on-line course about maths is the answer, > not documentation for a spreadsheet program. > > > In the bug-report the first comment complains that spreadsheet programs stick > to > > internationally agreed maths standard for the order in which to apply > functions, > > Bodmas (stands for "Brackets, of/division, multiplication, add, subtract"). > Choosing a non-standards order makes higher functions exponentially difficult > or > > even impossible. Before the 0 was borrowed from Arabic notation simple > multiplication and division was only possible by people with a university > degree > > level of maths skills. Choosing to go against Bodmas would be similarly > catastrophic. > > Business users like to left align numbers which makes simple addition more > difficult at a glance, for example > > £34 > £300 > ====== > £640 ?!!? > > Maths people and accountants tend to shudder at left aligned numbers, or > realise > > they are likely to make a lot of cash from these people. A right-justified > list > > makes it much more obvious > > £34 > £300 > ===== > £334 in a much more obvious way. Ok, its a stupid example with only 2 > numbers > in the list but imagine with a LOT more numbers in the list, say 20 to 30 per > page. > > > Back to the expected result of -9. What is the square root? -3 x 3 is not > really right. In fact we are now getting towards 2 dimensional numbers such > as > "imaginary numbers" and perhaps even getting close to chaos theory and > fractal > dimensions. > > > In the bug-report the first post shows a stunning lack of understanding about > maths, roughly along the lines of demanding that the spreadsheet program > should > give £640 in my example of adding numbers. > > > " > I definitly see this as a bug and confirm it. Here's what I did: > > 1: Input "=-3^2+4" into a spreadsheet cell, result is 13 > 2: Input "=4-3^2" into another cell, result is -5 > 3: Input "=-(3^2)+4" into a third cell, result is -5 > > The problem here seems to be that the program attaches the negative sign to > the > 3 in step one before doing the square, which it should not, unless manipulated > by parentheses like this: "(-3)^2". > " > > In 1 the result is 13 because the first function done is -3 x -3 = 9, and > then > add the 4 to give 13 > In 2 the result is due to an ambiguity that is normally resolved by using the > standards method of afaik 3 x 3 = 9, and then 4 - 9 = -5 People with maths > skills generally realise there is a potential problem with the ambiguity here > and might try fixing it by using brackets eg = 4 + (-3^2) which gives us 13 > 'obviously' since the inside of the bracket is done before applying the stuff > outside the brackets. > > In 3 the result is -5 because the bracketed stuff is done first giving us +9 > again, then outside the bracket that is made -+9 = -9 and then the 4 is added > as > expected. > > > This is maths, not spreadsheet stuff, unless i made a mistake in how #2 > should > be treated according to the Bodmas standards (in which case the bug-report > needs > to be fixed asap) but afaik i'm right. Even if i am wrong this is not really > a > job for documentation except as a brief note that 'common-sense' sometimes > over-rides Bodmas but will hopefully be fixed soon. > > Regards from > Tom :) > > > > > > ________________________________ > From: Regina Henschel <[email protected]> > To: [email protected] > Sent: Fri, 10 June, 2011 23:39:01 > Subject: Re: [libreoffice-documentation] Re: Collecting small things in the > Wiki > > Hi Tom, > Tom Davies schrieb: > >> Hi :) >> 3^2 does =9 ? >> > That's not the problem. But -3^2 result in 9 and that is the problem. > http://openoffice.org/bugzilla/show_bug.cgi?id=26755 > > Kind regards > Regina > > -- Unsubscribe instructions: E-mail to > [email protected] > Posting guidelines + more: http://wiki.documentfoundation.org/Netiquette > List archive: http://listarchives.libreoffice.org/global/documentation/ > All messages sent to this list will be publicly archived and cannot be deleted > > > Hi Tom. I think it is bedmas - brackets, exponentiation, division, multiplication, addition, subtraction. There will be a mathematical standard for this, so I suppose we are theorizing. To remove all doubt, if you wanted (-3)^2 you would use the brackets thus and if you wanted -(3^2) you would bracket that way. If there is no "Standard" then may be with a leading '-' sign LO should ask or auto correct to one of the bracketed options so it is clear what LO will do with the number. I have always taken -3^3 = -27 same as LO does now, was like that throughout university, but who is to say it is correct. steve
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