I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy

"Antonio Vernucci" wrote in message
.. .
I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy


I see it give the correct answers!!!

eg when A1 =2 the first formula =12 and the second =4

-2 squared =4
So 4 plus 8 = 12

2 squared =4
So 8 - 4 = 4

8 - (2 squared) = 4


Jeff

--
------------------------------------------------------
Antonio Vernucci, I0JX US call: K0JX
Beacons: 50.004 MHz & 70.088 MHz
Home page: http://www.qsl.net/i0jx
e-mail: k0jx {at} amsat {dot} org
------------------------------------------------------
"Jeff" ha scritto nel messaggio
. com...
"Antonio Vernucci" wrote in message
.. .
I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy


I see it give the correct answers!!!

eg when A1 =2 the first formula =12 and the second =4

-2 squared =4
So 4 plus 8 = 12

2 squared =4
So 8 - 4 = 4

8 - (2 squared) = 4

Yes, but the way Excel works is deceiving.

As a matter of fact, with reference to the general mathematical principle A+B =
B+A, let us have:
A= -A1^2
B = 8

Then, one would expect that -A1^2 + 8 is the same as 8 - A1^2, which is not the
way Excel works.

73

Tony I0JX

"Antonio Vernucci" wrote in
:

Subject: Be careful when using Excel
From: "Antonio Vernucci"
Newsgroups: rec.radio.amateur.antenna
Reply-To: "Antonio Vernucci"



--
------------------------------------------------------
Antonio Vernucci, I0JX US call: K0JX
Beacons: 50.004 MHz & 70.088 MHz
Home page: http://www.qsl.net/i0jx
e-mail: k0jx {at} amsat {dot} org
------------------------------------------------------
"Jeff" ha scritto nel messaggio
. com...
"Antonio Vernucci" wrote in message
.. .
I think this message can be of interest for those using Excel for
antenna calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2
(and not 2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy


I see it give the correct answers!!!

eg when A1 =2 the first formula =12 and the second =4

-2 squared =4
So 4 plus 8 = 12

2 squared =4
So 8 - 4 = 4

8 - (2 squared) = 4

Yes, but the way Excel works is deceiving.

As a matter of fact, with reference to the general mathematical
principle A+B = B+A, let us have:
A= -A1^2
B = 8

Then, one would expect that -A1^2 + 8 is the same as 8 - A1^2, which
is not the way Excel works.

So just what were you expecting to get? Were you expecting -A1^2 to
really be -(A1^2)?

-Bruce

On Sat, 09 May 2009 16:48:19 +0000, Jim Higgins
wrote:

The proper precedence of mathematical operations is "PEMDAS," meaning
Parenthesis, Exponentiation, Mult/Div, Add/Sub.

Yep. The MS precidence is:
http://support.microsoft.com/kb/25189/EN-US/

: Range
space Intersection
, Union
- Negation
% Percentage
^ Exponentiation
* or / Multiplication or Division
+ or - Addition or Subtraction
& Text Operator
= = = Comparison Operators

Note that the negation (negative sign) operator comes before any
arithmetic operators. The problem comes from Excel inventing some
kind of distinction between negation (negative number) and
substraction. For arithmetic, there is none. For C programmers,
there is a difference (in the way the data is stored). More on the
subject:
http://mathforum.org/library/drmath/view/69058.html

That minus in front of the A1 is a unary negation, which is a
multiplication by minus 1, so it should be performed AFTER the
exponentiation, i.e; -A1^2 = -(A1^2)

Excel performs it before the exponentiation, i.e.; -A1^2 = (-A1)^2

The Excel answer is incorrect.

Yep. However, MS is not about to create problems by fixing the
problem. It would be a bad thing to have existing spreadsheets,
suddently give different results when run on updated and fixed
versions of Excel. Compatibility with old bugs is one reason that
bugs tend to be perpetuated. Old bugs and sleeping dogs should be
left alone.

73 de Jim, KB3PU

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...
On Sat, 09 May 2009 16:48:19 +0000, Jim Higgins
wrote:

Yep. However, MS is not about to create problems by fixing the
problem. It would be a bad thing to have existing spreadsheets,
suddently give different results when run on updated and fixed
versions of Excel. Compatibility with old bugs is one reason that
bugs tend to be perpetuated. Old bugs and sleeping dogs should be
left alone.

73 de Jim, KB3PU


I sure am glad they finally fixed the simple calculator that Windows came
with. It had a major bug in it that if I remember correctly if you
substracted 3.1 from 3.11 you got zero. There were other numbers like that
also.

I think Intel had to recall a bunch of chips because of an error in the math
coprocessor part at one time.

Microsoft products are so full of 'problems' that if they ever put out an
error free product it would seem to be a mistake.

On Sun, 10 May 2009 16:19:22 +0000, Jim Higgins
wrote:

I disagree. Negation is not a subtraction operation; it's a
multiplication operation.

It varies by position. At the front of a string of arithmetic
operations, it's multiplication. In between the terms of an equation
or values, it's subtraction. This article covers some of the problem:
http://www.physicsforums.com/showthread.php?t=109516
Humans can usually make the distinction by context. Too bad computers
can't do the same.

Either way Microsoft Excel implements it incorrectly because in either
case exponentiation has a higher precedence in the science of
mathematics.

Agreed.

Agreed that it's too late to go back now, but bugs perpetuate because
they aren't fixed promptly when encountered. This issue isn't new and
it was fixable when first encountered in the very first release of
Excel.

I can sorta tolerate perpetuating mistakes. However, Microsoft's
attitude toward precedence operations reeks of damage control and of
trying to create a secondary standard by sheer number of users. The
first step to fixing the problem should have been to admit that they
were wrong. That never seems to have happened.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 8 May 2009 18:36:08 +0200, "Antonio Vernucci"
wrote:

I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy

In correct mathematical convention the expression
let A1 = 2 then

-A1^2 must yield

-A1^2 = -4

otherwise we would have to write
(-A1)^2 = 4

EXCEL does it the wrong way in example 1: =(-A1^2 + 8) = 12
and does it correctly in example 2 =(8 - A1^2) = 4.
But they are from Microsoft and they can do whatever they want.

w.

On Fri, 08 May 2009 20:59:35 +0200, Helmut Wabnig hwabnig@ .- --- -.
dotat wrote:

On Fri, 8 May 2009 18:36:08 +0200, "Antonio Vernucci"
wrote:

I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy

In correct mathematical convention the expression
let A1 = 2 then

-A1^2 must yield

-A1^2 = -4

otherwise we would have to write
(-A1)^2 = 4

EXCEL does it the wrong way in example 1: =(-A1^2 + 8) = 12
and does it correctly in example 2 =(8 - A1^2) = 4.
But they are from Microsoft and they can do whatever they want.

w.
TYPO correction
and does it correctly in example 2: =(8 - A1^2) = 4.

--
------------------------------------------------------
Antonio Vernucci, I0JX US call: K0JX
Beacons: 50.004 MHz & 70.088 MHz
Home page: http://www.qsl.net/i0jx
e-mail: k0jx {at} amsat {dot} org
------------------------------------------------------
"Helmut Wabnig" hwabnig@ .- --- -. dotat ha scritto nel messaggio
...
On Fri, 08 May 2009 20:59:35 +0200, Helmut Wabnig hwabnig@ .- --- -.
dotat wrote:

On Fri, 8 May 2009 18:36:08 +0200, "Antonio Vernucci"
wrote:

I think this message can be of interest for those using Excel for antenna
calculations.

Write in one cell: =(-A1^2 + 8) Note: the exponent of A1 is 2 (and not
2+8=10) because Excel performs squaring before summing

Write in another cell: =(8 - A1^2)

They look pretty much the same

But give A1 any non-zero value and see what happen.

73

Tony I0JX
Rome, Italy

In correct mathematical convention the expression
let A1 = 2 then

-A1^2 must yield

-A1^2 = -4

otherwise we would have to write
(-A1)^2 = 4

EXCEL does it the wrong way in example 1: =(-A1^2 + 8) = 12
and does it correctly in example 2 =(8 - A1^2) = 4.
But they are from Microsoft and they can do whatever they want.

w.
TYPO correction
and does it correctly in example 2: =(8 - A1^2) = 4.