I need to analyze my data using the Von Bertalanffy Growth function to my data (age vs Length). But I couldn’t figure out where and how to write my own non-linear regression model. Need help. My model is:
a*(1-exp(-(b*(age-c))))
Take a look at the documentation for the Nonlinear platform. The first section walks through an example to show exactly how to do this.
In short, after creating the column with your formula and parameters you put that column in the X, Predictor Role and your response column in the Y role.
The example you've given is from the Fit Curve platform. The output from Nonlinear is similar, though not exactly the same.
You can use the nonlinear platform (found under specialized modeling). a, b, and c should be entered as parameters (you need to supply initial values) and the platform will fit your model to your data - if it converges. If not, you might have to change your initial guesses for the parameters. If you haven't done this before, instead of entering variables in your formula, change the drop down menu from Table Variables to parameters.
Thanks for the reply. Could you please check the attached screenshots; I did not get any results
Please have a look at this too:
In the nonlinear launch, you need to put your predictor formula as "predictor" not the age variable.
Hi, ukhandurrani!
If you include a data table with your request for help (either yours or an example), the helpful responses you receive may be more implementable for you.
Kevin
