# Least Squares source code in C++?

1. Jul 10, 2008

### SirTristan

Does anyone know where to find source code for a simple and fast least squares solver written purely in C++?

2. Jul 11, 2008

### ice109

try the C++ version of LAPACK

3. Jul 11, 2008

### SirTristan

I actually already have LAPACK++ installed, however it's really pretty complicated. I'd like some simpler code that I can modify, for instance to implement regularization.

4. Jul 13, 2008

### zyh

you can find some code snippet in "Numerical Recipes in C book On-Line!"

http://www.fizyka.umk.pl/nrbook/bookcpdf.html [Broken]

and they are in Chapter 15.

Good luck.

Last edited by a moderator: May 3, 2017
5. Jul 14, 2008

### SirTristan

Thank you, that might be helpful.

Anyone know of algorithmic pseudocode for least squares anywhere, that I myself could use to create code? A http://en.wikipedia.org/wiki/Linear_regression#Example" can be estimated by solving for the (XTX)B=XTy normal equations, but that seems to be different than the decomposition and other approaches I've read about; and also I don't know how I'd be able to modify these normal equations for regularization purposes, as I don't see how the RSS can be modified. What I'm looking for is more of an iterative procedure.

Last edited by a moderator: Apr 23, 2017
6. Sep 4, 2008

### SirTristan

I'm having a problem trying to use the Levenberg-Marquardt source code from Numerical Recipes in C. The code requires the gaussj(float**, int, float**, int) function, and according to:
http://www.fizyka.umk.pl/nrbook/c0-2.pdf [Broken]

That is found in section 2.1. However, the http://www.fizyka.umk.pl/nrbook/bookcpdf.html" [Broken] gives a "file is damaged and could not be repaired" error when trying to open it. Does anyone know where I could find the code for this same gaussj() function? Thanks

Last edited by a moderator: May 3, 2017