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Exponential Curve Fitting

bwanders

Community Trekker

Joined:

Sep 20, 2013

Look at my attached file.  I have fitted an Exponential 3P curve to data that is based on %.  I have added a range check as well as a response limit for my "% knockdown" column.  I would like to have my fit curve parameter estimates not exceed 100%.  Is there a way to do this?

1 ACCEPTED SOLUTION

Accepted Solutions
mpb

Super User

Joined:

Jun 23, 2011

Solution

Instead of using the Fit Curve personality of Nonlinear, you can use the Custom Model personality (Help Index: Nonlinear Platform, Custom Models).

1. Create a column formula (say in column MyFormula) with parameters a, b and c:  a + b*exp(c*Time)

2. In the initial Nonlinear dialog Put MyFormula in the X, Predictor Formula box and %Knock Down in the Y, Response box. Then click OK.

3. In the second Nonlinear dialog you can click the red triangle by Nonlinear Fit and choose the first item, Parameter Bounds. You will then have the opportunity to supply Lower and/or Upper bounds for each of a, b, and c.

2 REPLIES
mpb

Super User

Joined:

Jun 23, 2011

Solution

Instead of using the Fit Curve personality of Nonlinear, you can use the Custom Model personality (Help Index: Nonlinear Platform, Custom Models).

1. Create a column formula (say in column MyFormula) with parameters a, b and c:  a + b*exp(c*Time)

2. In the initial Nonlinear dialog Put MyFormula in the X, Predictor Formula box and %Knock Down in the Y, Response box. Then click OK.

3. In the second Nonlinear dialog you can click the red triangle by Nonlinear Fit and choose the first item, Parameter Bounds. You will then have the opportunity to supply Lower and/or Upper bounds for each of a, b, and c.

bwanders

Community Trekker

Joined:

Sep 20, 2013

Thank you.  This nonlinear custom model definitley brought me to a new place in JMP.