Hello

Could it be possible to make linterp() deal with units? here's an example:


and a Mathcad example:


Cheers
Konrad

Yes Radovan, this can be done this way or another. The thing is, in engineering, the document has to be as simple and easy to understand as possible. Formulas have to be as presented in the rules. This is why Mathcad has gained so much popularity (and Smath is going similar way) in engineering: you produce a presentation-quality document right from the scratch. This document goes to many people, non-engineers, non-mathematicians, just various inspectors, authorities, managers, checkers (not associated with the project) etc. It's not about its strength in high maths. It's about clarity of the expression. I could write a C++ program doing my calculations, but I owe you a crate of slivovitsa if it's acceptable to anyone in the chain :-)

Yes, I know, sometimes it takes a lot of time to make something work with units, but when I do something without units, the frst thing that happens is the document gets rejected with a comment: please demonstrate the right units have been processed troughout the design. Mind you, Mars Climate Orbiter mission failed because of the units screwed up.
Another thing is, I as a design engineer need some degree of trust in my tools- I do make mistakes and it would be nice when my software warns me about it. Furthermore, I make calculation worksheets for the others, I have to be sure there is some foolproofness in what I give to my younger colleagues. It's not a big problem if it's about the length of my shoe laces, but when it comes to nuclear engineering, it makes the difference.

Regards
Konrad

Radovan,
Yes, it is a matter of taste when I do something for myself only, here and now. But let me give you an example. I make a lot of library functions, for general use not only for me. For instance, a function which returns design strength for a given material and temperature, something I tried to do in the first post of this thread. I wrote it in Mathcad so it can handle any temperature units, and it returns stress with units, so you can express it in the units of your choice. You can't fool it. Now imagine the same without units. The user needs to remember that the temperature has to be in deg C and the result in megapascals, not in bars for instance. That's ok, one thing to remember. Now what if there is a hundred of such functions, each of them used dosens of times in various places in the document and there is plenty of such documents which use different input data (from client's spec), which are in different units? I just don't want to have to remember about all this, because I'm sure I will forget one day.
The Mathcad example I gave was just a simplistic, quick check whether it works or not. In my case, I do something like in Smath example I showed in the beginning: a nice table which can be visually checked for errors. And what I like the most in Smath, this table contains reference data with units, which you can't do in Mathcad. It's just one small glitch, linterp() which can't swallow these units :-)

Regards
Konrad

Edited by user 24 November 2010 15:31:37(UTC)  | Reason: Not specified

Brilliant! That's a very good idea, define a new function! It fills the hole in my brain for today, thanks
Konrad