C++ curve fitting program, polyfit

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Hello,

I have been trying to curve fit a smooth and slightly oscillating curve. I have already tried to model this curve in MATLAB using the built in function 'polyfit' and to graph it using 'polyval'. Modeling and graphing using MATLAB was successful :) .

The ultimate goal of mine is to write this program in C++ in which I can model and retrieve polynomial coefficients using least squares fit. I was partially successful writing this program, however, the results compared to MATLAB result were not correct. I assume that the results I get from MATLAB is correct and this is a fairly good assumption for my case.

As a reference, I have used this sample program someone already has written, http://www.nr.com/forum/showthread.php?t=1452[^]. This program is evaluated using the headers from 'Numerical Recipes'.

I was wondering if there is any better way to approach the least squares fit problem. :confused:

Thank you for your time and hope to get some advise soon!

BM

Posted 31-May-10 7:32am

Jungyeoul Maeng

Updated 20-Sep-18 23:30pm

Deeksha Shenoy

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CPallini · Answer 1 · 2010-05-31T09:39:00

Solution 1

What does you mean, exactly with

Jungyeoul Maeng wrote:
I was partially successful writing this program, however, the results compared to MATLAB result were not correct

?

What is unsatisfactory in your fit?
:)

Posted 31-May-10 9:39am

CPallini

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Jungyeoul Maeng 2-Jun-10 9:55am

The result I get from MATLAB and C++ programs are off by as much as 30%. I believe that the curve fit from C++ does not quite match the ideal curve fit from MATLAB. I was looking for a more precise curve fit result from C++. Is there any reference I can take a look about least squares fit?

CPallini 2-Jun-10 14:04pm

How do you measure it (sorry for being nitpick)?

Hanso Handamp · Answer 2 · 2011-02-11T05:07:00

Solution 2

See http://www.slscope.co.uk/software/polyfit/index.html[^]

Posted 11-Feb-11 5:07am

Hanso Handamp