Can anyone think of a way to evaluate two polynomials into one equation?

[Bill_DuBose]

Can anyone think of a way to evaluate two polynomials into one equation?

I have two sequential, open-ended equations as follows:

Z(Y) = A₁Yⁿ + B₁Y^n-1 + C₁Y^n-2…

Where Y is described by:

Y(X) = A₂Xⁿ + B₂X^n-1 + C₂X^n-2…

I need one equation such that:

Z(X) = ???

What I am looking for is a process, maybe using linear algebra or matrix math to evaluate two equations into one.  I currently evaluate the first equation and then the second using the result of the first and this works fine, but if some “Summa Cum Nerdly” out there has a sneaky way to combine the process, the program will run more efficiently.  

[JeanPierre]

In LabVIEW >= 7.1 you  have the "Polynomial Composition.vi" that does that.

[chilly_charly]

Here is the solution suggested by JPD. I developped it because there is a trick if you want to use the Polynomial  Eval vi as it stands.

A better solution is to modify the subvi to make it accept a scalar as input.

Message Edité par chilly charly le 02-03-2006 07:01 PM

[JeanPierre]

No CC. I meant the VI located at Analyze>Mathematics>Polynomial>Polynomial Composition.vi.

The VI does not evaluate Z(Y(X)) for a given X but computes the polynomial coefficients of Z(Y(X)).

In LabVIEW >= 7.1 there is a set of VI to manipulate Polynomials as objects.

[chilly_charly]

Hooo ! you meant thaaaat ?

Thanks for the tip !

Message Edité par chilly charly le 02-03-2006 07:23 PM

[Ben]

"

“Summa Cum Nerdly”

"

Hmmm....

So if I had not gotten that "B" in psychology, I may have been able to answer this Q.

Ben

Only  "Magna Cum Nerdy"

[Bill_DuBose]

Thanks to all,  The routine that JPD sugested will perform nicely. I have a routine that allows the opperator to collect data.  The program then generates a best fit equation through the data.  The first table of data corelates the actual output signal to the nominal.  The second table correlates the nominal signal to the equivalent engineering units.  The two equations are then mapped together to produce a single calibration equation which is stored to disk as a string equation.  then on boot-up, the string is read into memory, converted into a parsed equation cluster and used to convert EU to electrical output and electical input to EU in my DAQ routine.