How can I re write this but with a different variable other than "syms"

Question

Owen Fernandez 2021-2-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/755084-how-can-i-re-write-this-but-with-a-different-variable-other-than-syms

回答： Walter Roberson 2021-2-26

syms x;
syms f(x);
% average of las 4 digitss
avg=4;
% get gama value
gama=5+avg;
% 5% relative error
err=5/100;
% defining the function
f(x)=(log(x)/log(exp(1)))*sin(x^2/(5*gama));
% lower limit of x
a=1;
% upper limit of x
b=11;
% goldain ratio
gr=(sqrt(5)+1)/2;
% new value for c and d using golden ratio , and
c=b-(b-a)/gr;
d=a+(b-a)/gr;
% to store number of iteration
itr=0;
% loop until opto 5% relative error
while abs((b-a)/a)>=err || abs((b-a)/b)>=err
  
% get functional value of c and d
val1=eval(f(c));
val2=eval(f(d));
% set new a or new b
if val1<val2
b=d;
else
a=c;
end
  
c=b-(b-a)/gr;
d=a+(b-a)/gr;
  
% increase iteration
itr=itr+1;
end
fprintf('Boundary is [ %.6f , %.6f ] after iteration %d\n',a,b,itr);
op_val=(a+b)/2;
fprintf('Optimal solution is %.6f\n',op_val);

I need to re-write this code without using the functions syms cause I do not have that for my matlab version.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Helen Liao 2021-2-26

编辑：Helen Liao 2021-2-26

Hi Owen,

I think there are two ways you can use

you can use function handle to do the same thing, and here is the doc link - https://www.mathworks.com/help/matlab/matlab_prog/creating-a-function-handle.html. For example, create a function handle like this in your script.

sqr = @(n) n.^2;

x = sqr(3)

Create a function to put your formula, and here is the doc link - https://www.mathworks.com/help/matlab/ref/function.html. just call the function in your script. Please be aware you need to put function in the same directory with your scrip or add the function to your path when you run your script. Otherewise it might not be able to find the function. Function example is like the following:

function ave = average(x)

ave = sum(x(:))/numel(x);

end

Hope those two methods could help you.

Thanks,

Helen

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2021-2-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/755084-how-can-i-re-write-this-but-with-a-different-variable-other-than-syms#answer_634394

在 MATLAB Online 中打开

% average of las 4 digitss
avg=4;
% get gama value
gama=5+avg;
% 5% relative error
err=5/100;
% defining the function
f = @(x) (log(x)./log(exp(1))).*sin(x.^2/(5*gama));
% lower limit of x
a=1;
% upper limit of x
b=11;
% goldain ratio
gr=(sqrt(5)+1)/2;
% new value for c and d using golden ratio , and
c=b-(b-a)/gr;
d=a+(b-a)/gr;
% to store number of iteration
itr=0;
% loop until opto 5% relative error
while abs((b-a)/a)>=err || abs((b-a)/b)>=err
  
% get functional value of c and d
val1 = f(c);
val2 = f(d);
% set new a or new b
if val1<val2
b=d;
else
a=c;
end
  
c=b-(b-a)/gr;
d=a+(b-a)/gr;
  
% increase iteration
itr=itr+1;
end
fprintf('Boundary is [ %.6f , %.6f ] after iteration %d\n',a,b,itr);
Boundary is [ 1.000000 , 1.031056 ] after iteration 12
op_val=(a+b)/2;
fprintf('Optimal solution is %.6f\n',op_val);
Optimal solution is 1.015528