MATLAB

Some basic MATLAB codes 

        Polyfit(Polynomial curve fitting)

Syntax
p=ployfit(x,y,n)
[p,S]=ployfit(x,y,n)
[p,S,mu]=ployfit(x,y,n)

p = polyfit(x,y,n) finds the coefficients of a polynomial p(x) of degree n that fits the data,p(x(i)) to y(i), in a least squares sense.

Example

x = (0: 0.1: 2.5)';
y = erf(x);
p = polyfit(x,y,6) 

The coefficients in the approximating polynomial of degree 6 are

p = 0.0084   -0.0983     0.4217     -0.7435    0.1471    1.1064   0.0004

There are seven coefficients, and the polynomial is

p=

Ref: http://www.mathworks.com/help/matlab/ref/polyfit.html

         Roots (Polynomial roots)

Syntax

r = roots(c)

r = roots(c) returns a column vector whose elements are the roots of the polynomial c.

Example

The polynomial s³ – 6s² – 72s – 27 is represented in MATLAB software as

p = [1 -6 -72 -27]

The roots of this polynomial are returned in a column vector by

r = roots(p)

r =    12.1229

        -5.7345

                -0.3884