function never used, I dont know why.

2021 7 17
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更新时间：2021 7 17
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I am using code from http://www.chuacircuits.com/matlabsim.php
%----------Chua.m----------
function out = chua(t,in)
x = in(1);
y = in(2);
z = in(3);
alpha = 15.6;
beta = 28;
m0 = -1.143;
m1 = -0.714;
h = m1*x+0.5*(m0-m1)*(abs(x+1)-abs(x-1));
xdot = alpha*(y-x-h);
ydot = x - y+ z;
zdot = -beta*y;
out = [xdot ydot zdot]';
%----------StartChua.m----------
[t,y] = ode45(@chua,[0 100],[0.7 0 0]);
plot3(y(:,1),y(:,2),y(:,3))
grid
end
It confuses me, cause obviously this code was already tested. matlab tells me now i have to put an "end" for the function, even tho the original code doesnt have one, ok I did it.
Then it tells me the function is never used, and [t,y] = ode45(@chua,[0 100],[0.7 0 0]); tells me that the function chua doesnt exist ?

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Star Strider
Star Strider 2021-7-17
Ran in:

1 个投票

Ran in:
In a script, all the function definitions must go at the end of the script:
%----------StartChua.m----------
[t,y] = ode45(@chua,[0 100],[0.7 0 0]);
plot3(y(:,1),y(:,2),y(:,3))
grid
%----------Chua.m----------
function out = chua(t,in)
x = in(1);
y = in(2);
z = in(3);
alpha = 15.6;
beta = 28;
m0 = -1.143;
m1 = -0.714;
h = m1*x+0.5*(m0-m1)*(abs(x+1)-abs(x-1));
xdot = alpha*(y-x-h);
ydot = x - y+ z;
zdot = -beta*y;
out = [xdot ydot zdot]';
end
That seems to work.
See Create Functions in Files for details.
.

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Martin Mayer
Martin Mayer 2021-7-17
Thank you for your answer.
I still get the error:
Unrecognized function or variable 'chua'.
Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Error in ode45 (line 115)
odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);
when I use this in command window:
[t,y] = ode45(@chua,[0 100],[0.7 0 0]);
plot3(y(:,1),y(:,2),y(:,3))
grid
Star Strider
Star Strider 2021-7-17
My pleasure!
It runs as posted in R2021a. It may be necessary to save the ‘chua’ function as ‘chua.m’ on your MATLAB search path with a version/release that does not support functions in files, specifically R2016a and earlier.
.
Martin Mayer
Martin Mayer 2021-7-17
I have R2020b. I tried other code before that used functions, it worked, but this one doesn't.
If function has same name as the script, it says Error: File: chua.m Line: 11 Column: 16
Local function name must be different from the script name.
Star Strider
Star Strider 2021-7-17
Since you have R2020b, if you copy and save the code I posted as a separate script (save it as whatever name you want), it should work just as it worked here.
I have no idea why it doesn’t work for you.
Also, try running the file I just attached. It ran without error when I tried it, and produced the desired result.
.
Martin Mayer
Martin Mayer 2021-7-17
Your file worked instant. I dont get it, but thanks. :)
Star Strider
Star Strider 2021-7-17
My pleasure!
If my Answer helped you solve your problem, please Accept it!
.

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