please someone solve this error ''Undefined function or variable 'x''.

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Meenakshi Tripathi
Meenakshi Tripathi 2021-7-22
编辑： Yongjian Feng 2021-7-22
function ross
L = [-1.0828 -1.6242;1.2513 1.8770;-0.0020 -0.0029];
master = [-x(2)-x(3);x(1)+0.5*x(2);2+x(3)*x(1)-4*x(3)];
slave = [-x(5)-x(6);x(4)+x(7)*x(5);2+x(6)*x(4)-4*x(6)]-L*y;
thetahat = 2*x(5)*[-0.2308 0.1538]*y;
y =[12*x(1)+2*x(2)+3*x(3)-12*x(4)-x(5)-3*x(6)-2*x(5)*thetahat;7*x(1)+3.5*x(2)+2*x(3)-7*x(4)-2*x(5)-2*x(6)-3*x(5)*thetahat]
x0 = [1 1 1 -5 -5 -5 0];
tspan= [0:0.001:70];
options = odeset('RelTol',1e-5,'AbsTol',1e-5);
[t,x]=ode45(@ross,tspan,x0,options)
function dxdt = ross(t,x)
dxdt = [master;slave;thetahat]
end
end
error is-
Undefined function or variable 'x'.
Error in ross (line 4)
master = [-x(2)-x(3);x(1)+0.5*x(2);2+x(3)*x(1)-4*x(3)];
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Rik
Rik 2021-7-22
If you have trouble with Matlab basics you may consider doing the Onramp tutorial (which is provided for free by Mathworks).

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Yongjian Feng
Yongjian Feng 2021-7-22
编辑：Yongjian Feng 2021-7-22
It seems like lines are all messed up. Do it make more sense to re-arrange them like this:
x0 = [1 1 1 -5 -5 -5 0];
tspan= [0:0.001:70];
options = odeset('RelTol',1e-5,'AbsTol',1e-5);
[t,x]=ode45(@ross,tspan,x0,options);
% This looks more like the function. Now x and t are input parameters, and
% they can be used inside the function
function dxdt = ross(t,x)
%function ross
L = [-1.0828 -1.6242;1.2513 1.8770;-0.0020 -0.0029];
master = [-x(2)-x(3);x(1)+0.5*x(2);2+x(3)*x(1)-4*x(3)];
y =[12*x(1)+2*x(2)+3*x(3)-12*x(4)-x(5)-3*x(6)-2*x(5)*thetahat;7*x(1)+3.5*x(2)+2*x(3)-7*x(4)-2*x(5)-2*x(6)-3*x(5)*thetahat];
slave = [-x(5)-x(6);x(4)+x(7)*x(5);2+x(6)*x(4)-4*x(6)]-L*y;
thetahat = 2*x(5)*[-0.2308 0.1538]*y;
%y =[12*x(1)+2*x(2)+3*x(3)-12*x(4)-x(5)-3*x(6)-2*x(5)*thetahat;7*x(1)+3.5*x(2)+2*x(3)-7*x(4)-2*x(5)-2*x(6)-3*x(5)*thetahat]
% The following lines moved up.
%x0 = [1 1 1 -5 -5 -5 0];
%tspan= [0:0.001:70];
%options = odeset('RelTol',1e-5,'AbsTol',1e-5);
%[t,x]=ode45(@ross,tspan,x0,options)
% function dxdt = ross(t,x)
dxdt = [master;slave;thetahat]
%end
end

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