Please help me how to run it :(

% MATLAB script file implementing the method of steepest descent
%Inputs:
%    x = starting vector 
%    xa, xb = x-interval used in contour plot 
%    ya, yb = y-interval used in contour plot 
%    tol = tolerance for stopping iteration
% Required m-file 
% fp.m is m-file for function f(x) 
% grad.m is m-file for gradient of f(x)
x=[-1.2;1.8];
xa=-1.5; xb=2; ya=-1; yb=2; xd=linspace(xa,xb,20);
yd=linspace(ya,yb,20); [X,Y]=meshgrid(xd,yd);
%% Example 1 Rosenbrock’s function 
% x=[-1.2, 1.8]; 
% xa=-1.5; 
% xb=2; 
% ya=-1; 
% yb=2; 
% steep; 
% Z=100*(X.^2-Y).^2+(X-1).^2;
%% Example 2
% x=[-1, 0.8]; xa=-1; xb=1; ya=-1; yb=1; steep; 
% x=[1, 0.8]; 
% x=[-0.8, -0.5]; 
% Z=(X-Y).^4+8*X.*Y-X+Y+3;
% Z=10*x^2+y^2;
tol=1.0*10^(-4); xpoints=x(1); ypoints=x(2); df=grad(x(1),x(2)); 

Unrecognized function or variable 'grad'.

dfx=df(1); dfy=df(2); df1=[dfx, dfy]; d1=-df1; q=1; counter=1; 
while norm(q)>tol 
    counter=counter+1; 
    s=fminbnd('fp',0,1,optimset('TolX',0.00001),x(1),x(2),d1(1),d1(2)); 
    q=s*d1; 
    xx=x+q'; 
    df=grad(xx(1),xx(2)); 
    dfx=df(1); dfy=df(2); 
    df1=[dfx, dfy]; 
    d1=-df1;
    x=xx;
    fprintf('\n %i Computed Solution = %e %e',counter,x);
    xpoints=[xpoints, x(1)]; 
    ypoints=[ypoints, x(2)]; 
    hold on 
    contour(X,Y,Z,30,'b') 
    plot(xpoints,ypoints,'ko-') 
    hold off
    pause
end
error=sqrt((1-x(1))^2+(1-x(2))^2);
fprintf('\n %i Computed Solution = %e %e Error = %e',counter,x,error);

There is error that says me 오류 발생: Steep_descent_method (30번 라인)

tol=1.0*10^(-4); xpoints=x(1); ypoints=x(2); df=grad(x(1),x(2));

How to solve it clearly?

[Torsten]

You missed to include grad.m and fp.m .

Answer 1

[Cris LaPierre]

The error is caused by this code: df=grad(x(1),x(2));

It can't find your m-file function grad.m. From your file comments (line 9)

% grad.m is m-file for gradient of f(x)

Make sure grad.m is in your current folder, or in a folder that has been added to your MATLAB path. See here:

https://www.mathworks.com/help/matlab/matlab_env/add-remove-or-reorder-folders-on-the-search-path.html