Steepest Ascent Method to Find Minimum - Error with syms to logical

I am attempting to find a minimum point, but I am receiving the following error for my code. I am unsure of how to work around this.

ERROR:

>> SteepestAscent

Conversion to logical from sym is not possible.

Error in SteepestAscent (line 10)

while es<ea && iter<itermax

MATLAB CODE:

function SteepestAscent()

iter=1;

itermax=5;

ea=5;

es=1;

x0=1;

y0=1;

%while (-6<x0) && (x0<6)

% while (-6<double(subs(y0))) && (double(subs(y0))<6)

while es<ea && iter<itermax

if (-6<x0) && (x0<6)

if (-6<double(subs(y0))) && (double(subs(y0))<6)

fx=4*x0^3+4*x0*y0+2*y0^2-42*x0-14; %Partial Deriv w/ X

fy=4*y0^3+2*x0^2+4*x0*y0-26*y0-22; %Partial Deriv w/ Y

%grad=[fx,fy];

syms h

x=x0+fx*h;

y=y0+fy*h;

f=x^4+y^4+2*x^2*y+2*x*y^2-21*x^2-13*y^2-14*x-22*y+170;

c=diff(f,h);

assume(h,'clear')

h=solve(c==0,h,'PrincipalValue',true);

x_new=x0+fx*h;

y_new=y0+fy*h;

ea=abs((x_new-x0)/x_new)*100;

x0=x_new;

y0=y_new;

end

end

iter=iter+1;

end

fprintf('X coordinate=')

disp(x0)

fprintf('Y coordinate=')

disp(y0)

end

Answer 1

[Samatha Aleti]

This error occurs when comparing a numeric value and a symbolic value. In order to compare these two values, you can convert symbolic value to numeric using “subs” function and “double” type-conversion.

The value "ea" will be symbolic values for the next iteration of while loop(in your code), Hence you can replace :

es < ea;

with

es<double(subs(ea)) ;

You can similarly replace when comparing other symbolic values with numeric values.