On 10/18/2006 11:06:08 AM, jmG wrote:
== The bad news for collabs who want to carry units in Mathcad is that all "dimensioned working formula" found in Engineering books have been made before Mathcad and made paper/pencil.
And, as evidenced by the examples I gave, they may not have been derived using the same units as the user of the formula. Hence, simply stuffing some numbers in them will give completely erroneous results. Ask NASA and ask them about F=ma at the same time.
== You can even carry your pet shop as units in Mathcad, so that 2 monkeys * 3 onions = monkey stew or onion soup .
What's wrong with that? Is there no place for Domestic Science in the Collaboratory?
== That's how I consider units in math software = an idiosyncrasy.
You are entitled to your opinion, however, rather than Fred et al, I find *your* arguments somewhat lacking in detail.
== That you might want to check if the paper/pencil conversion/relation is OK and use Mathcad unit capability = fine ! and then any formula designer should. But once that done, zap units in Mathcad work sheets and put the values appropriately and accordingly to the "dimensioned working formula"
Why? If the developed formula works and gives dimensionally correct results, why should anyone remove the units and risk introducing an error?
== The QED of this reply is that Units is the faith of the heretics and a useless luggage.
There is a scientific discipline, based in mathematics, known as Dimensional Analysis that deals with the algebra of quantity manipulation. Far from being the faith of 'heretics', I think you'll find that units are orthodoxy in engineering and scientific circles.
It's a good discipline for ensuring that you understand a formula and have accurately derived it. I have fond memories of Lecturer's being picked up on errors because somebody had noticed a dimensional inconsistency.
There have been several examples of this in the Collaboratory, where the correct use of units has identified an underlying problem. Philip Oakley's problem formula being one of the more recent (
http://collab.mathsoft.com/read?90107,11 ) - implementing h and D with units would have immediately shown that a problem existed, given reasonable guesses as to the nature of the quantities.
Stuart