MATLAB: Error : FSOLVE requires all values returned by functions to be of data type double.

error fsolvefsolve requires all values returned by functions to be of data type double (al)

I have faced with this error namely: FSOLVE requires all values returned by functions to be of data type double. Apparently, my mistake concerned to fsolve function.
I wonder if you tackle this problem. I write my code as follows:
clc
 clear all
 close all
   syms t y x1 x2 x3 x4 x5 x6 x7 x8 x9 x10
   f1(t)=input(' input function (  0<t<1  ) :  f1(t)= ' );
   f2(t)=input(' input function (  0<t<1  ) :  f2(t)= ' );
   b1(t,y)=input(' input function (  y=y(t) )  :  b1(t,y)= ' );
   b2(t,y)=input(' input function (  y=y(t) )  :  b2(t,y)= ' );
   a=0;
   b=1;
   n1=10;  %just an even number%
   m=100;
   n=100;
   Z1=[ x1 x2 x3 x4 x5 ];
   Z2=[ x6 x7 x8 x9 x10 ];
   A=zeros(n1/2,n1/2);
   for i=1:(n1/2)     
       for j=1:(n1/2)
           A(i,j)=int(t^i,0,1)*(2*i+3*j^2)/((1+i+j)^2);
           P(i,j)=(i^2-i*j+j^2)/((1+i*j)^2);
       end            
   end 
   A
   P
i=1;
for j=1:m
    dt=(b-a)/n;
    dB1=sqrt(dt)*randn(1,n);
    B=cumsum(dB1);
      for k=1:(n1/2)
          Q1(k)=B(k*n/n1);
          Q2(k)=B((k+5)*n/n1);
      end
       Q1
       Q2
      F(t)=Z1*A(:,i)-b1(t,f1(t)+Z1*P*A(:,i))+Z2*Q1'-b2(t,f2(t)+Z2*P*Q2');        
      for l=1:n1 
          Eqs(l)=F(2*l-1)/(2*n1);  
          x=[x1,x2,x3,x4,x5,x6,x7,x8,x9,x10];
      end
      f=@(x)[Eqs(1) , Eqs(2) , Eqs(3) , Eqs(4) , Eqs(5) , Eqs(6) , Eqs(7) , Eqs(8) , Eqs(9) , Eqs(10)];
      x0=[0 0 0 0 0 0 0 0 0 0];
      w(i,:)=fsolve(f,x0)         
      i=i+1;
  end              
MW=mean(w);
SW=std(w);
L=MW-1.96/sqrt(m)*SW
U=MW+1.96/sqrt(m)*SW
————————————————
Please input the functions as you wish.
For example: f1(t)=f2(t)=t , b1(y,t)=b2(y,t)=y+t ;
————————————————-
Thank you in advance.

Best Answer

If you have a symbolic expression then you need to use vpasolve rather than fsolve.
Alternatively you can use matlabFunction to convert the symbolic expression into a function handle that can be used with fsolve. If you do this and you have more than one input variable to be solved for then be sure to use the 'vars' option of matlabFunction
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