I have two equations with two variables each is a function of another, so I'm using ''fsolve'' for solving two nonlinear equations. but if I have an equation with a specific constant which I want to give it a range (e.g. 1:50)

function F = root2d(x,n) 

F(1)= x(1)-1+((1-x(2))^n);

F(2)= (x(2)*(33*(1-2*x(1))+32*x(1)*(1-(2*x(1))^3)))-2*(1-(2*x(1)));

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I want to obtain the values of two variables x(1),x(2) at each value of n which takes a range (i.e. 1--->50).

How can I do that?

[madhan ravi]

can you elaborate what's x and n? give some examples

Answer 1

[Stephan]

Hi,

i guess you are searching for this (rename the outer function or save it as some_stuff_with_n.m in your matlab search path:

function some_stuff_with_n

sol = zeros(50,2);

      for k = 1:50
          n = k;
          sol(k,1:2) = fsolve(@root2d,[1, 1]);
      end

      function F = root2d(x,~)
          F(1) = x(1)-1+((1-x(2))^n); 
          F(2) = (x(2)*(33*(1-2*x(1))+32*x(1)*(1-(2*x(1))^3)))-2*(1-(2*x(1)));
      end
  end

This calculates the function root2d 50x for n=1...50, calculates the x(1) and x(2) values corresponding to this n and saves it in the variable you want. Use:

sol = some_stuff_with_n

to call it.

Best regards

Stephan

[Ahmed Ibrahim]

Very thanks for your help.But how I can obtain x(1),x(2) values? because I want to calculate a final parameter S that is a function of x(2) and n,so we can have the values of S corresponding to each x(2),n,i.e. having 50 value for S. How can I obtain x(1),x(2),and corresponding S values?

[Stephan]

x(1) and x(2) are stored in sol(:,1) and sol(:,2). Every row index corresponds to the Value of n. In column 1 there is x(1) and in column 2 there is x(2).

[Ahmed Ibrahim]

I know that, the problem is that when running this code,I do not get sol() in workspace. Just 'the eq. is solved' appears. And when I call the function, the error 'too many arguments' appears

[Walter Roberson]

Change the first line to

function sol = some_stuff_with_n

[Ahmed Ibrahim]

Thank you very much

[madhan ravi]

Accept the answer if your question has been solved.

[Ahmed Ibrahim]

Ok, thanks.