2Var app - user defined fit
04-29-2014, 07:54 AM (This post was last modified: 04-29-2014 07:55 AM by Angus.)
Post: #1
 Angus Member Posts: 212 Joined: Feb 2014
2Var app - user defined fit
hello,

How would I use a user defined equation for fitting in the Statistics 2Var App? Say I have 3 points in the num view. Choosing between the predefined types in the symbolic view works fine, but when I change the equation the type changes to 'User Defined' as expected, but no fitting is done. I've tried Fit1: A*X^2+B as equation instead of the predefined quadratic type.

I noticed that changing the type requires a switch to plpot view to take effect and recalculate the fitting. Is that desired?

thanks
04-29-2014, 12:22 PM (This post was last modified: 04-29-2014 12:23 PM by Han.)
Post: #2
 Han Senior Member Posts: 1,810 Joined: Dec 2013
RE: 2Var app - user defined fit

In sum, a user-defined fit is not the same as one of the built-in fits. A user-defined fit merely allows the user to take an already-existing fit and make minor adjustments to the formula (hence it becomes "user-defined"). Think of it as a means to tweak an existing formula obtained from one of the built-in fits in order to obtain a function that more closely resembles the data.

Graph 3D | QPI | SolveSys
04-29-2014, 02:38 PM
Post: #3
 Tim Wessman Senior Member Posts: 2,206 Joined: Dec 2013
RE: 2Var app - user defined fit
Han's link is correct. I would just add that it would also be used so students could enter a custom fit and try to "manually" fit the data.

Note that I would like to make a way to enter an arbitrary function for curve fitting at some point though. You'd probably have to give it initial values for all the variables and there would be no guarantee of success, but that is how it is with generic curve fitting.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
04-29-2014, 03:10 PM
Post: #4
 Angus Member Posts: 212 Joined: Feb 2014
RE: 2Var app - user defined fit
Thanks guys. Sorry, I just didn't notice the other thread.

Seems like I misunderstood the given app. Tim's idea seems interresting to me. It might not be of major practical usage because most common functions are present, but it might come in handy occasionally. Plus it is fun.
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