MATLAB: M-file function for solving high order polynomial equation

solve

I want to build for solving polynomial equation for high order (example x^202+x^102+x^52+100) and apply other problem.

I write m-file in this form.

function [eig] = solvepoly(chareq)

eq = 'chareq';
eig = solve(eq);

end

Then I use this function. The answer isn't correct.

>> [eig] = solvepoly(@(x) x^2+2*x+1)

eig =

But I use this command in command window. I get this answer.

>> eq = 'x^2+2*x+1'; >> eig = xolve(eq)

eig =

-1 -1

Help me please.

Best Answer

This is easier:

syms x
p = x^202+x^102+x^52+100;
r  = roots(sym2poly(p));

The ‘r’ variable will have all 202 roots.

Related Solutions

MATLAB: How Can I define a Polynomial of degree n with symbolic coefficients

Whats the problem? This seems clear.

syms x a b c
P = a*x^2+b*x+c;

Are you looking for a general solution for any n? This seems to work:

n = 3;
syms x
P = sym('a',[1,n+1])*x.^(n:-1:0).'
P = 
  a1*x^3 + a2*x^2 + a3*x + a4

MATLAB: M-file function

Your function is calling itself without approaching any convergance or something that will allow it to end. Therefore it will run forever and eventually out of memory (hence the error). Try splitting it up into a script and a function as so:

Script:

 %creating window of plot from -5 to 50 using stepsize 0.25 for t x-axis
 %t should be on the x axis, v should be on the y axis
 k=0; 
for i= -5:.25:50
    k = k+1;
    t(k)=i;
    v(k)=vPieceWise(t(k));
end 
plot(t,v);
 
figure
plot(t,v);
hold on

Function:

%Part A: Mfile function to compute v as a function of t
function v = vPieceWise(t)
 if (t < 0)
        v = 0;
    elseif (0 <= t)&&(8<=16)
        v = -5*t+10*t.^2;
    elseif (8<=16)&&(t<=16)
        v = 624 - 3*t;
    elseif (t<=16)&&(t<=26)
        v = 12*(t-16).^2+36*t;
    elseif (26<t)
        v = 2136*exp(-0.1*(t-26));
 end

Best Answer

Related Solutions

MATLAB: How Can I define a Polynomial of degree n with symbolic coefficients

MATLAB: M-file function

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