Ошибка в матлабе unrecognized function or variable

rihana_jeth asked . 2023-01-13

I am receiving one of the following error messages. How can I resolve this issue?

Undefined function or variable ‹Name›.
Unrecognized function or variable ‹Name›.
Undefined function or method ‹Name› for input arguments of type ‹ClassName›.

undefined , function , variable , error , Language Fundamentals , Entering Commands

Kshitij Singh answered . 2023-06-13 21:56:32

MATLAB does not recognize the specified string as the name of a function on the MATLAB path or as a variable. The above error messages can be caused by:

1) Trying to use a variable that has not been defined before this line of code executes.

>> x=1:10;
>> t=x.^2;
>> plot(x,y)
Undefined function or variable 'y'.
% Possible corrections:
% Change line 3 to "plot(x,t)"
% or Change line 2 from "t=x.^2;" to "y=x.^2;"

2) A typographical error when typing a function or variable name. However, later versions of MATLAB try to resolve these typos with “Did you mean” suggestions. For example,

>> foo = 42;
>> fo0
Undefined function or variable 'fo0'.
Did you mean:
>> foo

3) The wrong case for a function or variable name. Later versions of MATLAB try to resolve these typos with “Did you mean” suggestions.

4) Changing directories so that a function you used is no longer on the MATLAB path.

5) Trying to use a function for which you are not licensed or that belongs to a MathWorks toolbox that isn’t installed. In later versions of MATLAB, this is not an “Undefined function or variable” error, and MATLAB lets you know that you are either not licensed to use the function or the appropriate toolbox is not installed.

6) Trying to use a function that belongs to a third-party toolbox that isn’t installed.

7) Trying to use a function that does not yet exist in your version of MATLAB.

Trying to use a function that has been removed from your version of MATLAB. In later versions of MATLAB, this is not an “Undefined function or variable” error, and MATLAB lets you know the new, preferred function to use.

9) Trying to use a variable that gets cleared from the workspace because your script or function contains «clear all» or «clearvars».

10) Calling an object method without an object as the first input.

11) Using a MEX function that is compiled on a platform different from the one in use.

Not satisfied with the answer ?? ASK NOW

I am trying to plot a three dimensional phase portrait of a system of first order differential equations, but I am getting an error message saying I have an unrecognized variable eta. Apart from the three dimensional phase portrait, I also want to plot x(1) versus t, x(2) versus t, and x(3) versus t, all on the same graph. I have commented out this plot command because I’m sure I’m wrong. So, I am looking to plot (i) a 3D phase portrait, and (ii) a time plot of x(1), x(2) and x(3) all on the same graph. Also, the [-0.015,0.015], [-2,2], [-4,4] that you see in the argument of the ode45 are the axes limits of x(1), x(2) and x(3). I am not even sure that the axes limits should be placed there. Could someone please help? Thank you.

[t,x] = ode45(@eqx3, eta, omega, [-0.015,0.015], [-2,2], [-4,4], initcond);
global eta omega
eta = 0.05;
omega = 25;
%tspan = [0,50]
initcond = [1, 0.5, -0.4]


%subplot(211)
%plot(t, x(:,1), t,x(:,2),'--',x(:,3),'--');
%xlabel('t')

subplot(212)
plot(x(:,1), x(:,2), x(:,3))
xlabel('x1')
ylabel('x2')
zlabel('x3')

function xdot = eqx3(t,x,eta,omega)
  global eta omega
  xdot = zeros(3,1);
  xdot(1) = -(2*eta*omega + 1)*x(1) + x(2) - 1;
  xdot(2) = -(2*eta*omega + (omega^2))*x(1) + x(3) + 2;
  xdot(3) = -(omega^2)*x(1) + x(2) - 1;
  %xdot =[xdot(1);xdot(2);xdot(3)];
end