How to generate a best fit curve Z = aX^bY^c

[nanay001]

Hello,

I have a set of data which I divided into 3 vectors X, Y, and Z. I am trying to generate a best fit equation for this data based on the formula Z = a*X^b*Y^c

Is there a function in Mathcad to determine a best-fit equation based on the above formula.

This question was posted before, but was lost when the PTC Community forum got migrated into a new platform, so I am trying to get back the answers I obtained.

Thanks,

Felipe Loo

[Werner_E]

You may have a look at the Mathcad function "genfit".

EDIT:: genfit will not work with 2 independent variables. The multidimensional analogon in Mathcad is "multidfit".

Or you could use a solve block with "minerr"

EDIT: I didn't look too closely at the type of your equation. Now that I did I guesss that Alan's suggestion below is the best appraoch. You may use "polyfit"/"polyfitc" to do so.

[AlanStevens]

Or take logs and use a linear fit.

Alan

[ValeryOchkov]

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@nanay001 wrote:

Hello,

I have a set of data which I divided into 3 vectors X, Y, and Z. I am trying to generate a best fit equation for this data based on the formula Z = a*X^b*Y^c

Is there a function in Mathcad to determine a best-fit equation based on the above formula.

This question was posted before, but was lost when the PTC Community forum got migrated into a new platform, so I am trying to get back the answers I obtained.

Thanks,

Felipe Loo

---

Sorry, it will be not a curve but a surface.

Give please us please your 3 vectirs!

[ValeryOchkov]

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@nanay001 wrote:

Hello,

I have a set of data which I divided into 3 vectors X, Y, and Z. I am trying to generate a best fit equation for this data based on the formula Z = a*X^b*Y^c

Is there a function in Mathcad to determine a best-fit equation based on the above formula.

This question was posted before, but was lost when the PTC Community forum got migrated into a new platform, so I am trying to get back the answers I obtained.

Thanks,

Felipe Loo

---

Sorry, it will be not a curve but a surface.

Send please please your 3 vectirs!

[Werner_E · Accepted solution]

Here are some suggestions as to how to achieve what you demanded for.

[ValeryOchkov]

See please the article

Price of an Old Car Or The way from Correlation to Regression in Mathcad