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EETStoodent1-Visitor
1-Visitor
February 15, 2011
Question

I'm not a happy camper. Mathcad 15 trial download AND paid box version both have the same undefined variable error bug?

  • February 15, 2011
  • 3 replies
  • 18804 views

MWSnap 2011-02-14, 16_58_53.jpg

I spent an entire week out of my life neglecting my responsibilities while probing the mathcad help menus and tutorials and quicksheets so I could figure out what I'm doing wrong. I'm not doing anything wrong. I've included my latest worksheet as proof. I can't believe mathcad does not have an option for updates in the help menu like every other reputable software company on the planet. Am I going to have to search for some kind of update file on the ptc website to fix the bugs that come with the Mathcad 15 software that I paid for? I sincerely hope I will not have to purchase a yearly maintenance plan so that I can get basic bug fixes for "The Global Standard for Engineering Calculations."

3 replies

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f.kohlhepp1-Visitor
1-Visitor
February 15, 2011

It's not broke; and it's not wrong.

The red and error are symptoms of your call to the symbolic processor. But the evaluation of Z_1 iss correct.

If you type Z_1:=R_1+L_1 and enter there will be no red, and Z_1--.>will get you the proper answer.

Red errors and symbolic processes are not new.

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EETStoodent1-VisitorAuthor
1-Visitor
February 16, 2011

::sigh:: Okay, here we go. Here is a better example of the Mathcad 15 bug that I'm trying to describe.

MWSnap 2011-02-15, 19_20_12.jpg

Just because a bug isn't new doesn't mean it's not broke and it's not wrong. If this bug has existed for a long time and it still has not yet been fixed then the people who work at Mathcad should really be ashamed of themselves. "The product development company" "The Global Standard for Engineering Calculations." Seriously?

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RichardJ19-Tanzanite
19-Tanzanite
February 16, 2011

It is not a bug. When you use the explicit keyword you are asking the symbolic processor to replace the variable with it's numeric value. In this case, it can't, because the symbolic processor sees ohms as an undefined variable. The symbolic processor does not know about units. That is a limitation, but it''s not a bug. Since PTC (or previously Mathsoft) did not write the symbolic engine there is little they can do about that.

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RichardJ19-Tanzanite
19-Tanzanite
February 15, 2011

Why are you doing a symbolic evaluation followed by a numeric evaluation (if you are not aware of the distinction please say so, and you will get the 5 minute introduction)? The symbolic processor does not know about units, and that is the source of your problem. If you do a symbolic evaluation you see the symbol for Ohms, but it's not the unit of resistance, it's just an undefined variable. The symbolic processor does not care about undefined variables (after all, it does symbolic math!) but the result from the symbolic prrocessor is then passed to the numeric processor, which does care about undefined variables. If you want a numeric evaluation, use the numeric evaluation operator. If you want a symbolic evaluation use the symbolic evaluation operator, but always be aware that the symbolic processor does not know about units.

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EETStoodent1-VisitorAuthor
1-Visitor
February 16, 2011

It's all about the presentation. That is the whole reason I'm trying to use Mathcad instead of Mathematica or Matlab or Maple, all products which are vastly superior to Mathcad in just about every way you can imagine except when it comes to easily presenting the data the way that math PhD's want to see the data.

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wayne12-Amethyst
12-Amethyst
February 16, 2011

Well,

I learned Turbocad before Autocad, thought Autocad was not as good, unitl I got used to it. Now there's RIVIT, which is vastly better, except when it's not. Then must go back to Autocad.

I learned STAAD before SAP, then ROBOT, thought ROBOT was not as good, until I go used to it.

Then I learned RISA, it was better for the user and faster to learn that ROBOT, but not as general, and not as general as SAP either, but for everyday use, was better. So when RISA is not apporpriate , I go to one of the others.

A sledge hammer is more powerful and general than a finishing hammer, but If I was building a shelf I would rather have the finishing hammer.

( Just a saying, I am not necessarily saying that Mathcad is a finishing hammer compared to the others, but to suggest that the right tool for the job is not always the same tool)

Mathcad is by far the better tool for production work that must be documented and reviewed by others.

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RichardJ19-Tanzanite
19-Tanzanite
February 15, 2011

I spent an entire week out of my life neglecting my responsibilities while probing the mathcad help menus and tutorials and quicksheets so I could figure out what I'm doing wrong.

As a tip for the future, your attempt at solving the problem by looking in the help is admirable. It is actually quite annoying when someone posts a question here that could have been answered easily by just looking in the help or Quicksheets. But there comes a time when the best thing to do is post a question to these forums, and perhaps that's at less than the one week point

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EETStoodent1-VisitorAuthor
1-Visitor
February 16, 2011

Yes, I'm really good at obsessing over a problem that seems like it should be easy enough to solve until I finally find the answer (days later LOL). I've been 100% sure that the answer to this problem exists just right around the next corner if I just open up the next quicksheet or the next help file. I've actually spent a lot of my time trying to engineer a work around to trick the software into doing what I want it to do since it was actually working part of the time. It was like somebody was playing a prank on me. This was all with the 30 day trial download that I wasted a week of my life. I shouldn't say wasted because now I'm really good at using a lot of the features of mathcad since I learned those features while searching for the solution that I was never able to find.

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mzeftel1-Visitor
1-Visitor
February 18, 2011

Hello,

I've gone through the posted worksheets, and Richard's example clearly shows the bug. I've logged the bug for both Mathcad 15 and the issue for the new version of the software, Mathcad Prime 1.0, as we implement symbolics in it.

As Richard pointed out, symbolics and explicit don't currently handle units, so you see some issues. He provided some workarounds for you.

We prioritize bugs for each release. It may seem easy to you to fix this issue, but units aren't implemented in symbolics, which makes it more complex.

If you recently purchased Mathcad 15, you also received a license for Mathcad Prime 1.0. We will be adding symbolics to Mathcad Prime.

Mathcad Prime 1.0 has both dynamic units, and units added to most functions, plots, and tables. It also allows mixed units in matrices, which is not a feature of previous versions of Mathcad. As we add symbolics to Mathcad Prime, we'll be adding improvements to it as well.

I hope this helps answer your questions.

And I'm glad you were able to learn many features of Mathcad through your investigation.

Best regards,

Mona

Mathcad Senior Technical Consultant

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