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3-Visitor

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

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

1 ACCEPTED SOLUTION

Accepted Solutions
24-Ruby V
(To:nanay001)

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

6 REPLIES 6
24-Ruby V
(To:nanay001)

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.

16-Pearl
(To:Werner_E)

Or take logs and use a linear fit.

Alan

24-Ruby III
(To:nanay001)

@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.

24-Ruby III
(To:nanay001)

@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.