# LabVIEW

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## solution for the system of equations

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?

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## Re: solution for the system of equations

@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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Message 2 of 9
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## Re: solution for the system of equations

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?

Message 3 of 9
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## Re: solution for the system of equations

@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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CEO: What exactly is stopping us from doing this?
Expert: Geometry
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Message 4 of 9
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## Re: solution for the system of equations

@Norbert_B wrote:

I assume that 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

Message 5 of 9
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## Re: solution for the system of equations

Hii Nobert,

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

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## Re: solution for the system of equations

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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CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.
Message 7 of 9
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## Re: solution for the system of equations

Bob is correct. I clearly explained in question. It is a system of linear equations with 4 unknowns x1, x2, x3 & x4.

Message 8 of 9
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## Re: solution for the system of equations

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

Message 9 of 9
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