Re: Calculation Operator ">" not ">=" !!

On Tue, 23 Oct 2007 18:12:30 -0700, monir wrote:

On Oct 22, 2:29 am, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
On Sun, 21 Oct 2007 21:03:33 -0700, monir wrote:
On Oct 21, 10:28 pm, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
On Sun, 21 Oct 2007 10:44:02 -0700, monir wrote:
Hello;
I was a bit hesitant to post this question for obvious reasons, but I
decided to post it anyway!! You never know!
I've two real variables: A & B. The MS application has the following
built-in comparison operators to choose from:
<= , = , >= , int(eger)
One may choose one or more operators from the above list.

I need to specify : A > B

Is there an intelligent way of doing so ???
(choosing the constraint A >= B appears to force the built-in
procedure to first try A = B and fails)

Thank you.
Monir

_What_ Microsoft application? There's a lot of them.

A > B = not(A <= B).

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html-Hide quoted text -

- Show quoted text -

Hi Tim;
1. It's MS Excel 2003 add-in Solver module.

Your first mistake is probably to try to coerce Excel into doing something
real, but I'm not much of an Excel fan.

2. For the current Solver optimization scenario to be successful, it
must satisfy the constraint A1 > B1 (together with the other specified
constraints).
3. Solver has the following comparison operators to choose from in
"Subject to the Contraints" box: <= , = , >= , int(eger), bin
One may choose one or more operators from the above list.

Can you turn the problem around such that you're tasking Excel to look for
<= instead of >? You may also want to consider that with floating point
operations it'll be a rare problem indeed that will solve with '>' that
won't work with '>='.

4. A glimmer of hope might reside in the fact that the Solver
constraint box allows for a formula to be entered and not only a
numerical value or a cell reference. Somehow, one might be able to
manipulate the available conditions { <=, =, >=, int } together with
some Excel functions and end up with the constraint A1 >
B1 !!!!!!!!!!!

I think that's more than a glimmer. That may be your best bet.

5. Depending on the problem parameters, a successful solution by
Solver could yield a value in A1 that's a fraction or many-order-of-
magnitude greater than the value in B1.

Your expert suggestion would be greatly appreciated.
Monir

I'm no expert, but I will say that if you're going to be doing much real
mathematical analysis there are much better platforms out there to do it on
than any spread***. A programmatic analysis tool like Scilab, MATLAB,
Octave or R comes to mind, as well as a free-form spread*** tool such as
MathCad, or (I believe) Maple or Mathematica. Any of the alternatives I
mention are far superior to Excel for doing real work, and Scilab, Octave
and (I believe) R are all available for free.

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -

- Show quoted text -


Tim;
1. Excel and its VBA are practical and reasonable analytical tools as
long as they work properly, and the add-in module Solver is quite
adequate for the problem at hand.

2. The Solver problem with ">=", or "<=" for that matter, is
associated with the "or equal to" in the two comparison operators.
Solver appears to start with it and subsequently fails.

3. The desired condition "A1 > B1" CAN NOT be replaced by "A1 >= B1 OR
"A1 >= B1+something". A singular behaviour exists at A1=B1, and thus
the condition doesn't exist. Keep in mind that the correct solution
could yield A1 value to be a fraction or many-order-of-magnitude
greater than B1.

4. I've done some additional analytical work on the condition A1 > B1
and been able to reformulate the problem such that the constraint is
no longer required. The number of constraints now is less by one.

5. Solver now works correctly and as desired, yet I'm still curious to
why ">", "<", and/or "<>" are not included in the comparison operators
box !! I'm sure, if asked, MS would/could provide a lengthy and
complex reasoning!!

6. Since you're familiar with these analytical packages: Scilab,
MATLAB, Octave, R, MathCad, Maple and Mathematica:
which of these "free" tools would you recommend for Academia/
Scientists/Engineers ?? .. Links ??
I suppose any of them would be good enough tool to have for spot-check
or answer-on-the-fly!!
Few months ago and following a recommendation, I made an inquiry to
Mathematica. They never replied. Most likely, they're out of
business!

Thank you kindly.
Monir

Personally I use Scilab 99% of the time, with occasional use of MathCad.
Scilab is free, but MathCad is in the $500/seat range -- and probably
worth it. AFAIK Maple and Mathematica are very similar to MathCad -- in
fact, MathCad uses the Maple engine for symbolic computations.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.