Check the type of the F-array you calculate at the end of your code. My guess is that it's not of type double (as required by fsolve), but of type symbolic.
Best wishes
Torsten.
FSOLVE requires all values returned by functions to be of data type double.
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dear all i write code like below that produce 9*1 matrix that have 9 sym variable x1,x2,.........,x9 i m using fsolve to calculate these variable :
function F = consnt4(x)
m=1.669e-3;
jx=5.743e-14;
E=2.1e11;
O=12.5e-3;
jz=1.149e-13;
G=8e10;
L=3e-3;
g=1;%9.81;
N=3;
T1=5;
T2=0;
T3=0;
syms real
q = sym('q', [1 N+1], 'real');
eb = sym('eb', [1 N+1], 'real');
teta = sym('teta', [1 N+1], 'real');
tetad = sym('tetad', [1 N+1], 'real');
ebd = sym('ebd', [1 N+1], 'real');
qd = sym('qd', [1 N+1], 'real');
x =sym('x', [1 3*N+1], 'real');
r(:,:,1)=[1*O;0;0;];
r(:,:,2)=[(-1/2)*O;(sqrt(3))*O/2;0];
r(:,:,3)=[(-1/2)*O;-(sqrt(3))*O/2;0];
for i=2:N+1
pl(:,:,i)=L*[(cos(q(i))*(1-cos(teta(i))))/teta(i);(sin(q(i))*(1-cos(teta(i))))/teta(i) ; sin(teta(i))/teta((i))];
Rl(:,:,i)=[cos(q(i))*cos(teta(i))*cos(eb(i)-q(i))-sin(q(i))*sin(eb(i)-q(i)) -cos(q(i))*cos(teta(i))*sin(eb(i)-q(i))-sin(q(i))*cos(eb(i)-q(i)) cos(q(i))*sin(teta(i)); sin(q(i))*cos(teta(i))*cos(eb(i)-q(i))+cos(q(i))*sin(eb(i)-q(i)) -sin(q(i))*cos(teta(i))*sin(eb(i)-q(i))+cos(q(i))*cos(eb(i)-q(i)) sin(q(i))*sin(teta(i));-sin(teta(i))*cos(eb(i)-q(i)) sin(teta(i))*sin(eb(i)-q(i)) cos(teta(i))];
R(:,:,2)=Rl(:,:,2);
R(:,:,1)=[1 0 0;0 1 0;0 0 1];
p(:,:,2)=pl(:,:,2);
end
for i=3:N+1
R(:,:,i)=R(:,:,i-1)*Rl(:,:,i);
p(:,:,i)=p(:,:,i-1)+R(:,:,i-1)*pl(:,:,i);
end
for i=2:N+1
wl(:,:,i)=[-sin(q(i))*tetad(i)-cos(q(i))*sin(teta(i))*cos(teta(i))*qd(i)+cos(q(i))*sin(teta(i))*ebd(i);cos(q(i))*tetad(i)-sin(q(i))*sin(teta(i))*cos(teta(i))*qd(i)+sin(q(i))*sin(teta(i))*ebd(i);((sin(teta(i)))^2)*qd(i)+cos(teta(i))*ebd(i)];
w(:,:,2)=wl(:,:,2);
end
for i=3:N+1
w(:,:,i)= w(:,:,i-1)+R(:,:,i-1)*wl(:,:,i);
end
for i=2:N+1
for j=2:i
wc(:,:,i)=collect(w(:,:,i),[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]) ; % ;,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
end
end
for i=2:N+1
for j=1:size(w(:,:,i),1)
[wtemp,vtemp]=coeffs(wc(j,:,i),[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]);% ,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
[~,idx]=ismember(vtemp,[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]);% ,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
wk(j,idx,i)=wtemp;
end
end
for i=2:N+1
pd(:,:,i)=[teta(i)*((-qd((i))*sin(q(i))*(1-cos(teta(i)))+tetad(i)*sin(teta(i))*cos(q(i)))+tetad(i)*(L*cos(q(i))*(1-cos(teta(i)))))/(teta((i))^2); teta(i)*((qd((i))*cos(q(i))*(1-cos(teta(i)))+tetad(i)*sin(teta(i))*sin(q(i)))+tetad(i)*(L*sin(q(i))*(1-cos(teta(i)))))/(teta((i))^2); (teta(i)*tetad(i)*cos(teta(i))-tetad(i)*L*sin(teta(i)))/(teta(i)^2)];
v(:,:,2)=pd(:,:,2);
end
for i=3:N+1
v(:,:,i)= v(:,:,i-1)+cross(w(:,:,i-1),R(:,:,i-1)*pl(:,:,i))+R(:,:,i-1)*pd(:,:,i);
end
for i=2:N+1
for j=2:i
vc(:,:,i)=collect(v(:,:,i),[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]);%,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
end
end
for i=2:N+1
for j=1:size(v(:,:,i),1)
[vwtemp,vvtemp]=coeffs(vc(j,:,i),[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]);%,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
[~,idx]=ismember(vvtemp,[qd(2),tetad(2),ebd(2),qd(3),tetad(3),ebd(3),qd(4),tetad(4),ebd(4)]);%,qd(5),tetad(5),ebd(5),qd(6),tetad(6),ebd(6),qd(7),tetad(7),ebd(7),qd(8),tetad(8),ebd(8),qd(9),tetad(9),ebd(9)]);
vk(j,idx,i)=vwtemp;
end
vk(:,3*(i-1),i)=[0;0;0];
end
for i=N+1
Mb(:,:,i)=E*jx*((teta(i))/L)*R(:,:,i-1)*[-sin(q(i));cos(q(i));0];
Mt(:,:,i)=-G*jz*eb(i)*R(:,1,i)/L;
Me(:,:,i)=Mt(:,:,i)-Mb(:,:,i);
end
for i=2:N
Mb(:,:,i)=E*jx*((teta(i))/L)*R(:,:,i-1)*[-sin(q(i));cos(q(i));0];
end
for i=2:N
Mt(:,:,i)=-G*jz*eb(i)*R(:,1,i)/L;
end
for i=3:N+1
Mtt(:,:,i)=G*jz*eb(i)*R(:,1,i)/L;
end
for i=2:N
MT(:,:,i)=Mt(:,:,i)+Mtt(:,:,i+1);
end
for i=2:N
Me(:,:,i)=Mb(:,:,i+1)-Mb(:,:,i)+MT(:,:,i);
end
for i=2:N+1
Fg(:,:,i)=-m*g*[1;0;0];
end
for i=2
ph(:,1,i)=[pl(:,:,i)+R(:,:,i)*r(:,:,1)-r(:,:,1)];
ph(:,2,i)=[pl(:,:,i)+R(:,:,i)*r(:,:,2)-r(:,:,2)];
ph(:,3,i)=[pl(:,:,i)+R(:,:,i)*r(:,:,3)-r(:,:,3)];
end
for i=3:N+1
ph(:,1,i)=[R(:,:,i-1)*pl(:,:,i)+R(:,:,i)*r(:,:,1)-R(:,:,i-1)*r(:,:,1)];
ph(:,2,i)=[R(:,:,i-1)*pl(:,:,i)+R(:,:,i)*r(:,:,2)-R(:,:,i-1)*r(:,:,2)];
ph(:,3,i)=[R(:,:,i-1)*pl(:,:,i)+R(:,:,i)*r(:,:,3)-R(:,:,i-1)*r(:,:,3)];
end
for i=2:N+1
ap(:,:,i)=[sqrt(ph(1,1,i)^2+ph(2,1,i)^2+ph(3,1,i)^2);sqrt(ph(1,2,i)^2+ph(2,2,i)^2+ph(3,2,i)^2);sqrt(ph(1,3,i)^2+ph(2,3,i)^2+ph(3,3,i)^2)];
f(:,:,i)=[ph(:,1,i)/ap(1,1,i) ph(:,2,i)/ap(2,1,i) ph(:,3,i)/ap(3,1,i)];
end
for i=N+1
Fc(:,:,i)=[-T1*f(:,1,i) -T2*f(:,2,i) -T3*f(:,3,i)];
end
for i=2:N
Fc(:,:,i)=[T1*f(:,1,i+1) T2*f(:,2,i+1) T3*f(:,3,i+1)]+[-T1*f(:,1,i) -T2*f(:,2,i) -T3*f(:,3,i)];
end
for i=2:N+1
fa(:,:,i)=Fc(:,1,i)+Fc(:,2,i)+Fc(:,3,i);
end
for i=2:N+1
Ma(:,:,i)=cross(r(:,:,1),Fc(:,1,i))+cross(r(:,:,2),Fc(:,2,i))+cross(r(:,:,3),Fc(:,3,i));
end
for i=2:N+1
feq(:,:,i)=fa(:,:,i); +Fg(:,:,i);
Meq(:,:,i)=Ma(:,:,i); + Me(:,:,i);
end
for i=2:N+1
for j=2:N+1
vk(:,:,i)=subs(vk(:,:,i),q(j),x(j-1));
wk(:,:,i)=subs(wk(:,:,i),q(j),x(j-1));
Meq(:,:,i)=subs(Meq(:,:,i),q(j),x(j-1));
feq(:,:,i)=subs(feq(:,:,i),q(j),x(j-1));
end
end
for i=2:N+1
for j=2:N+1
vk(:,:,i)=subs(vk(:,:,i),eb(j),x(j+2));
wk(:,:,i)=subs(wk(:,:,i),eb(j),x(j+2));
Meq(:,:,i)=subs(Meq(:,:,i),eb(j),x(j+2));
feq(:,:,i)=subs(feq(:,:,i),eb(j),x(j+2));
end
end
for i=2:N+1
for j=2:N+1
vk(:,:,i)=subs(vk(:,:,i),teta(j),x(j+5));
wk(:,:,i)=subs(wk(:,:,i),teta(j),x(j+5));
Meq(:,:,i)=subs(Meq(:,:,i),teta(j),x(j+5));
feq(:,:,i)=subs(feq(:,:,i),teta(j),x(j+5));
end
end
for j=1:(3*N)
for i=2:N+1
F(j,:,:)= dot(Meq(:,:,i),wk(:,j,i))+dot(feq(:,:,i),vk(:,j,i));
end
end
and after that i try
x0=[0;0];
options = optimoptions('fsolve','Display','iter');
[x,fval] = fsolve(@myfunn,x0,options)
but i got error : FSOLVE requires all values returned by functions to be of data type double. cod that you see seems to be complex but it is just some simple multiplication of matrix and there is no integration i really appreciated if you could help it is the matter of life and death
5 Comments
Accepted Answer
Steven Lord
on 19 Dec 2017
If you want to solve a system of equations symbolically or using symbolic variables, use the solve function instead of fsolve. The fsolve function requires that the output of the function you specify as the first input be double precision numbers, not symbolic expressions.
If you must use fsolve with symbolic variables inside the function, you must convert those symbolic expressions into numbers using double before returning the numbers (not the symbolic expressions) from the function.
As a very simple example, put all this code into a function example373677.m and run it:
function y = example373677
y = fsolve(@mysubfun, 3);
function z = mysubfun(q)
x = sym('x');
r = x.^3-2*x-5;
z = double(subs(r, q));
Of course, with solve this is easier.
syms x
y = solve(x.^3-2*x-5)
You may need to use vpa to approximate y numerically.
vpa(y)
One of the solutions returned in y should match the result you received from running the function.
More Answers (2)
Matt J
on 19 Dec 2017
that have 9 sym variable x1,x2,.........,x9 i m using fsolve to calculate these variable :
FSOLVE does not work with sym variables. It only works with normal variables.
6 Comments
Matt J
on 19 Dec 2017
Edited: Matt J
on 19 Dec 2017
OK, well, here's my quick tutorial on the difference between normal variables in MATLAB and symbolic variables.
When I refer to a "normal" variable, I mean a variable that is used to store a number, usually in floating point form.
>> x=3
x =
3
I think it's fair to say that this is the most common kind. When you store a number to a variable, calculations with that variable result in other numbers, e.g.,
>> y=x+pi
y =
5.1416
Symbolic variables, however, do not store numbers. They store expressions. They are created using syms() rather than by assigning numbers to them. When you do calculations with symbolic variables, they result in other symbolic variables or expressions, e.g.,
>> syms xs
>> ys=xs+pi
ys =
xs + pi
You can use the subs() command to seemingly substitute numbers into symbolic variables, but the result is still an expression, not an actual number,
>> ys=subs(xs+pi,3)
ys =
pi + 3
To tell the difference between a symbolic variable and a normal variable, you can use whos()
>> whos x y xs ys
Name Size Bytes Class Attributes
x 1x1 8 double
xs 1x1 8 sym
y 1x1 8 double
ys 1x1 8 sym
In the "Class" column you can see that xs and ys are sym variables, wheres x and y are double floating point numbers. You can also use the class() command to get similar information.
Symbolic variables and expressions which evaluate to numbers can be converted to normal double floating point variables using the double() command, e.g.,
>> double( subs(xs+pi,3) )
ans =
6.1416
Finally, not all MATLAB commands are built to deal with symbolic variables. FSOLVE is one of them. It expects that your consnt4() function will return an F value that is a floating point number, not a symbolic expression. So you have two choices: either get rid of all the symbolic computation in consnt4() or make sure that F gets converted to type double before you return it. The former is usually the better choice. It is not clear why you need to do any symbolic computation for your task. Normal floating point computation looks like it will be fine.
Krishna Kant
on 5 Jul 2021
clc
clear all
close all
for k=1e-3:1e-3:10e-3
x_0=0;
[n,fval] = fsolve(@(x) dispersion(x,k), x_0);
end
% peakgrowthwavenumber = ((rho2-rho1)*a/S)^0.5
% growthrate = transpose(growthrate);
% wavenumber = transpose(wavenumber);
function F = dispersion(x,k)
D=1;
mu1=1e-5;
rho1=1;
rho2=1000;
mu2=1e-3;
S=1e-9;
h=D;
a=1;
q1 = (k^2+(x(1)*rho1/mu1))^0.5;
q2 = (k^2+(x(1)*rho2/mu2))^0.5;
A = [1 -1 1 -1 -1 -1;
k k q1 q2 -k -q2;
0 exp(-k*h) 0 exp(-q2*h) exp(k*h) exp(q2*h);
0 -k*exp(-k*h) 0 -q2*exp(-q2*h) k*exp(k*h) q2*exp(q2*h);
2*mu1*(k^2) -2*mu2*(k^2) mu1*(q1^2+k^2) -mu2*(q2^2+k^2) -2*mu2*(k^2) -mu2*(q2^2+k^2);
rho1+(a*k/(x(1)^2))*(rho1-rho2+(k^2*S/a))+(2*(k^2)/x(1))*(mu1-mu2) rho2 (a*k/(x(1)^2))*(rho1-rho2+(k^2*S/a))+(2*k*q1/x(1))*(mu1-mu2) 0 -rho2 0];
F = det(A)==0;
end
Error Message:
Error using fsolve (line 281)
FSOLVE requires all values returned by functions to be of data type double.
Error in dispersioneqnSolving (line 9)
[n,fval] = fsolve(@(x) dispersion(x,k), x_0);
My problem is same I am having a sym variable. What is the way to avoid this error and make this code working. I need to use fsolve as its a non-linear solver. solve and vpasolve sometimes fail for various parameters.
Any help will be deeply appreciated.
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