Error Using ode45, trying to call a function into ode45? please help

Question

Abdurahman Itani 2017-10-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/362693-error-using-ode45-trying-to-call-a-function-into-ode45-please-help

评论： Walter Roberson 2017-10-23

 clc;
clear;
m1 =250; m2=40; c1=2000; k1=15000; k2=150000;
duf =@(t,y) [y(2);
    1/m1*(c1*(y(4)-y(2))+k1*(y(3)-y(1)));
    y(4);
    1/m2*(-c1*(y(4)-y(2))-k1*(y(3)-y(1))+k2*(@yfunction-y(3)))]
    [t,y] =ode45(duf,[0,4.5 ], [0; 0;0;0]);

and I am trying to call this piecewise function

function [f] = yfunction(T)
% Define time and function for the 1st interval
t1=[0:0.0005:0.05];
f1=4.*t1;
% Define time and function for the 2nd interval
t2=[0.05:0.0005:0.3];
f2=0.2*ones(size(t2));
% Define time and function for the 3rd interval
t3=[0.3:0.0005:0.35];
f3=-4.*(t3-0.35);
T= [t1 t2 t3];
f= [f1 f2 f3];

this is the error i am recieving

Undefined operator '-' for input arguments of
type 'function_handle'.
Error in
problem2>@(t,y)[y(2);1/m1*(c1*(y(4)-y(2))+k1*(y(3)-y(1)));y(4);1/m2*(-c1*(y(4)-y(2))-k1*(y(3)-y(1))+k2*(@yfunction-y(3)))]
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);
Error in problem2 (line 10)
[t,y] =ode45(duf,[0,4.5 ], [0; 0;0;0]);

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Answer 1

Nicolas Schmit 2017-10-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/362693-error-using-ode45-trying-to-call-a-function-into-ode45-please-help#answer_287173

在 MATLAB Online 中打开

There is an error in

duf = [... @yfunction-y(3) ... ]

You are calling @yfunction without any argument. The correct syntax might be

@yfunction(y(3))

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Walter Roberson 2017-10-23

That would not be valid. yfunction(y(3))-y(3) would be valid (but not sure it would be correct for the case. Maybe yfunction(t)-y(3) ... or something else.)

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