llsq, a MATLAB code which solves the linear least squares (LLS) problem. It finds the "best" straight line to match a set of data points. More precisely, it finds the quantities "a" and "b" defining the straight line y=a*x+b, which minimizes the root-mean-square (RMS) error to the data.


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.


llsq is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and Programs:

fmincon_test, a MATLAB code which illustrates the use of fmincon, a function included in MATLAB's Optimization Toolbox, which seeks the minimizer of a scalar function of multiple variables, within a region specified by linear constraints and bounds.


test_approx, a MATLAB code which defines test problems for approximation, provided as a set of (x,y) data.

test_lls, a MATLAB code which implements linear least squares (LLS) test problems of the form A*x=b.


  1. David Kahaner, Cleve Moler, Steven Nash,
    Numerical Methods and Software,
    Prentice Hall, 1989,
    ISBN: 0-13-627258-4,
    LC: TA345.K34.

Source Code:

Last revised on 15 January 2019.