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MITHOOON

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06-08-2016 04:48 AM

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I have the following system of equations:

90x1+85x2+55x3+52x4=900;

2.5x1+4.5x2+35x3+34x4=800;

Since the number of unknowns are more than the number of equations, the system is underdetermined. So it has infinite number of solutions. But I need only the positive solutions. That is, the valuse of the unknwns should be greater than zero. Is there any way to find the solution in labview?

Norbert_B

Proven Zealot

06-08-2016 07:07 AM

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@MITHOOON wrote:

[...] Is there any way to find the solution in labview?

Sure there is.... if you write a program which does this. LV is a programming language, not a mathematical script solver.

Before going into implementation, you have to know how you want to achieve a result.

For example: You could implement a program which plots the result of the first equation, left part, depending on X. You could mark all instances in the graph where the value equals 900.

Repeat this for the second equation. Any X which is a valid solution for first AND second plot is a result you are looking for.

There are, however, better methods. Most of them are listed in technical literature.....

Norbert

Norbert

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Alexander_Sobolev

Active Participant

06-08-2016 09:59 AM - edited 06-08-2016 10:02 AM

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What do you call a solution?

4D matrix with marked surface? = list of (x1, x2, x3, x4) values on some grid.

Analytical description of the surface (expressions of the lines limiting 2D flat surface in 4D space)?

Program that gives you x1 and x2 if you set other variables?

Norbert_B

Proven Zealot

06-08-2016 10:27 AM

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@Alexander_Sobolev wrote:

What do you call a solution?

4D matrix with marked surface? = list of (x1, x2, x3, x4) values on some grid.

Analytical description of the surface (expressions of the lines limiting 2D flat surface in 4D space)?

Program that gives you x1 and x2 if you set other variables?

I **assume** that this should not be x1, x2, x3,... but x^1, x^2, x^3, ...

OP: Could you clarify?

Norbert

Norbert

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Bob_Schor

Knight of NI

06-08-2016 12:15 PM - edited 06-08-2016 12:16 PM

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@Norbert_B wrote:I

assumethat this should not be x1, x2, x3,... but x^1, x^2, x^3, ...OP: Could you clarify?

Norbert

Norbert,

I think x1 is x-sub-1, not x-to-the-first-power. It looks like he's trying to solve a system of linear equations, where there are fewer equations than unknowns (4 unknowns, x1, x2, x3, x4 a.k.a. x, y, z, and w).

BS

06-10-2016 01:48 AM

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Hii Nobert,

How to plot an equation with 4 unknowns?!!! 4D plot?

Norbert_B

Proven Zealot

06-10-2016 02:37 AM

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If Bob is correct, the proposal with the graph is of course quite difficult.

However, the question is more a generic computer science question (building an algorithm or find suitable existing methods) rather a LV question.

Norbert

Norbert

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06-10-2016 04:01 AM

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Bob_Schor

Knight of NI

06-10-2016 07:29 AM

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As has already been stated, the basic question being posed is a question in __mathematics__, not __LabVIEW__. Some "math" software (I'm thinking of some of the "M" languages, such as Mathematica, Maple, and MathCad) probably have ways to __set up__ problems in under-determined Linear Equations subject to constrains, and employ "under-the-hood algorithms" to solve this type of problem, but (to the best of my knowledge) LabVIEW does not. If you can set up the problem appropriately, you can (probably) __code__ the (iterative) algorithm using LabVIEW, but the bulk of your effort will be learning how to solve this type of problem, namely the __math__ involved. Once you know and understand this, translating this to an algorithm should be relatively straight-forward.

In short, LabVIEW is not necessarily the ideal platform for this question.

Bob Schor