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ytang-21-Visitor
1-Visitor
August 18, 2013
Question

Recursive symbolic function derivation

  • August 18, 2013
  • 3 replies
  • 7280 views

Hi, I met a problem when deriving a recursive symbolic function by MATHCAD, the orginal functions read:

1.jpg

2.jpg

3.jpg

What I want is to derive the following recursive functions:

4.jpg

As function gn(t) will be becoming very complex, the rest of deviration work has to accomplished by computer, but I don't know how perfectly Mathcad can handle this problem. So if anyone has any avice, I will be extremely grateful!

3 replies

W
Werner_E25-Diamond I
25-Diamond I
August 18, 2013

What about your last question here http://communities.ptc.com/message/211709#211709 ?

Also you should state which version you use and attach the worksheet to show what you have done so far.

Y
ytang-21-VisitorAuthor
1-Visitor
August 19, 2013

As you kindly stated, MathCAD seems to have weak functionalities on vectors of functions. I tried to simplify the functions to the way you suggested, however each of them is very complicated and the bound of my function vector is dynamic. So in the end I decide to leave this issue to MATLAB (I am not sure whether it will work) even I prefer the output forms by MathCAD much better.

Back to the current question, I want to derive the equations in MathCAD as the derived function form is more intuitive. Attached is my MathCAD file built on MathCAD v15. It seems to me that MathCAD can't derive the formulas in a recursive way. As you see in my last post, actually the function mu(t) is finally replaced by function B and vanished consequently. If you can give me some suggestions, that will be very thankful.

A
AlanStevens19-Tanzanite
19-Tanzanite
August 19, 2013

Is the attached any help? Mathcad won't do it symbolically, but numerically seems ok.

Alan

W
Werner_E25-Diamond I
25-Diamond I
August 25, 2013

As Mathcad seems not be able to do the job, maybe using SMath (http://smath.info) could be a solution. It seems not implement that late binding of variables in symbolic mode and so we get the results demanded. Unfortunately the ability to symbolically simplify expressions (like simplify, expand, or factor) are nonexistent in SMath (yet).

recur_symb3.png

W
Werner_E25-Diamond I
25-Diamond I
August 27, 2013

To round it up after a long downtime of the Forum and to test that awful sounding new moderation scheme which I fear will be responsible for unaccaptable time delays, I attach a modified sheet in both SMath and Mathcad format.

In SMath the result was copied and assigned a variable and the sheet then exported in XMCD format. After some modifications in Mathcad the results are now useable in MC for simplification ot whatever you had in mind.

recur_symb4.png

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