Assignment variables for Laguerre's Method Program

I have the following Laguerre's Method program in MATLAB but I am having trouble with the assignment. Can someone show me how to assign some function, say x^6-5x-88, with a starting value at x0=2 and a tolerance level of say, 10^-10. Do note that I did not write this program but found it online. Since I am theoretically studying Laguerre's Method, I thought it would be good for me to see how the method works in practice rather than using paper and pencil. Any detailed help is appreciated as this would be my first time using MATLAB. Here is the code (and it can be found here as well http://www.pcs.cnu.edu/~bbradie/matlab/rootfinding/polyroots.m): Do note that I just want to know how you assign the function, any function, into the program, set your starting value and set the tolerance level. Thanks.

function r = polyroots ( poly, Nmax, TOL )

%POLYROOTS locate the roots of an arbitrary polynomial using Laguerre's % method % % calling sequences: % r = polyroots ( poly, Nmax, TOL ) % polyroots ( poly, Nmax, TOL ) % % inputs: % poly vector containing the coefficients of the polynomial % whose roots are to be computed. the first entry in % the vector must be the leading coefficient of the % polynomial, and the final entry must be the constant % term. zero coefficients must be explicitly provided. % Nmax maximum number of iterations to be performed to % compute each root % TOL absolute error convergence tolerance % % output: % r vector containing the roots of the polynomial % % NOTE: % if POLYROOTS is called with no output arguments, the % roots of the polynomial and the number of iterations % required to compute each root are displayed % % if the maximum number of iterations is exceeded, a message % to this effect will be displayed and the roots for which % convergence had been achieved will be returned %

q = poly; degree = length(poly)-1; r = zeros ( 1, degree ); its = zeros ( 1, degree ); found = 0;

while ( found < degree - 2 ) [new, done] = laguerre ( q, 0.0, TOL, Nmax );

    if ( done == 0 )
       disp('Maximum number of iterations exceeded')
       return
    end;

    if ( abs(imag(new)) == TOL )
       found = found + 1;
       r(found) = real(new);
       its(found) = done;
       q = deconv ( q, [ 1 -real(new) ] );
    else
       r(found+1) = new;
       r(found+2) = conj(new);
       its(found+1) = done;
       its(found+2) = done;
       found = found + 2;
       q = deconv ( q, conv ( [1 -new], [1 -conj(new)] ) );
    end;
    q = real(q);
end;

if ( found == degree - 2 ) if ( q(2) == 0 ) r(degree-1) = sqrt ( -q(3)/q(1) ); r(degree) = -r(degree-1); else r(degree-1) = 2*q(3) / ( -q(2) - sign(q(2)) * sqrt ( q(2)*q(2) - 4*q(1)*q(3) ) ); r(degree) = q(3) / ( r(degree-1) * q(1) ); end; else r(degree) = -q(2)/q(1); end;

if ( nargout == 0 ) disp ( [r' its'] ) end;

function [y, done] = laguerre ( f, x0, TOL, Nmax )

done = 0; n = length ( f ) - 1; fp = polyder ( f ); fp2 = polyder ( fp );

for i = 1 : Nmax fx = polyval ( f, x0 ); fpx = polyval ( fp, x0 ); fp2x = polyval ( fp2, x0 );

    if ( abs(fx) < TOL ) 
       y = x0; done = i;
       return
    end;

    gx = fpx / fx;
    g2 = gx * gx;
    hx = g2 - fp2x / fx;

    disc = sqrt ( (n-1) * ( n * hx - g2 ) );
    if ( abs(gx-disc) < abs(gx+disc) )
       denom = gx+disc;
    else
       denom = gx-disc;
    end
    dx = n / denom;
    x0 = x0 - dx;

    if ( abs(dx) < TOL ) 
       y = x0; done = i;
       return
    end 
end
y = x0;