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ptc-61415841-Visitor
1-Visitor
June 6, 2014
Solved

solution to ODE system

  • June 6, 2014
  • 2 replies
  • 1746 views

Hello, everyone.

I want to solve a somehow complicated ODE system of 5 equations. But the Software seems have problem to solve it.

If I change the y5 in the 4th line of my DD matrix, it can be solved. But the results are definitely what I expected.

Please check the attachment for the situation.

So the questions are:

1. Why the MathCAD have problem with solving my origenal matrix?

2. what change I need to make to get the results?


Best answer by Werner_E

Vector elements are numbered beginning with 0 by default (is controlled by system variable ORIGIN) and so there is no element nr 5 in your vector y (which consists of just 5 elements 0,1,..4).

You have used index 0, 1, 3, 4 and 5. This would assumer either a vector with 6 elements or maybe, as you haven't used index 2, you are supposed to decreement the last 3 indices by 1.

2 replies

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Werner_E25-Diamond IAnswer
25-Diamond I
June 6, 2014

Vector elements are numbered beginning with 0 by default (is controlled by system variable ORIGIN) and so there is no element nr 5 in your vector y (which consists of just 5 elements 0,1,..4).

You have used index 0, 1, 3, 4 and 5. This would assumer either a vector with 6 elements or maybe, as you haven't used index 2, you are supposed to decreement the last 3 indices by 1.

P
ptc-61415841-VisitorAuthor
1-Visitor
June 6, 2014

thanks, this is like the first MathCAdD I write after switch from MatLab. What a natural mistak. lol!

A
AlanStevens19-Tanzanite
19-Tanzanite
June 6, 2014

y has 5 components numbered 0 through 4. There is no component number 5. In DD you have not used y2; I guess it should be there somewhere and you should only be referencing numbers 0 to 4 (remember that, by default, Mathcad starts numbering vectors from zero).

Alan

Edit: Werner just beat me to it!

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ptc-61415841-VisitorAuthor
1-Visitor
June 6, 2014

Thanks very much!

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