i have error in this code while using ode45

2022 5 23
1 个回答
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更新时间：2022 5 27
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%constants
A=2.6e-3;
B=90;
C=0.025;
D=5.0E-3;
E=0.3;
F=0.0041;
G=0.27;
H=83.7;
%Parameter Changes
A1=2.6e-2;
B1=80;
C1=0.025;
D1=6.0E-3;
E1=1;
F1=0.008;
G1=0.27;
H1=83.7;
%hold on
f=@(t,y) [-y(2) y(1) -A(y(1)-B); C*D*(y(3)-E) -C*y(2); -G*y(3) +F*max(0,y(1)-H)];
[t,xa]=ode45(f, [0 180], [250 :0 350]);
Index exceeds the number of array elements. Index must not exceed 1.

Error in solution (line 26)
f=@(t,y) [-y(2) y(1) -A(y(1)-B); C*D*(y(3)-E) -C*y(2); -G*y(3) +F*max(0,y(1)-H)];

Error in odearguments (line 92)
f0 = ode(t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 107)
odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
disp(t,xa);
f=@(t,y) [-y(2) y(1) -A1(y(1)-B1); C1*D1*(y(3)-E1) -C1*y(2); -G1*y(3) +F1*max(0,y(1)-H1)];
[t,xb]=ode45(f, [0 180], [250 0 350]);
disp(t,xb);
figure(1)
plot(t,xa(:,1)+50,"LineWidth",2); ylabel("glucose(mm/dl)");
xlabel("time(min)");title('Glucose dynamics')
hold on
plot(t,xb(:,1),"LineWidth",2); ylabel("glucose(mm/dl)");
xlabel("time(min)");title('Glucose dynamics')
legend ('Orignal','Dexcom Curve')
hold off
%hold on
figure(2)
plot(t,xa(:,2)*33,"LineWidth",2); ylabel("Interstitial insulin(\uU/ml)");
xlabel("time(min)");title('Interstitial insulin dynamics')
hold on
plot(t,xb(:,2),"LineWidth",2); ylabel("Interstitial insulin(\uU/ml)");
xlabel("time(min)");title('Interstitial insulin dynamics')
legend ('Orignal','Dexcom Curve')
hold off
figure(3)
plot(t,xa(:,3)+5,"LineWidth",2); ylabel("Plasma insulin(\uU/ml)");
xlabel("time(min)");title('Plasma insulin dyanmics')
hold on
plot(t,xb(:,3),"LineWidth",2); ylabel("Plasma insulin(\uU/ml)");
xlabel("time(min)");title('Plasma insulin dyanmics')
legend ('Orignal','Dexcom Curve')
hold off

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 采纳的回答

Walter Roberson
Walter Roberson 2022-5-23
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Ran in:
[250 :0 350]
ans = 350
Your vector of initial conditions only has one entry.
Your line of code will not be interpreted as
[250, :0, 350]
and that would be a syntax error if it was.
Likewise it is not interpreted as [250 :0: 350] -- which would give you an empty vector.
The 250 :0 part is being intepreted as (250:0) -- the vector of values starting with 250, incrementing by 1, and ending with the first number that is greater than 0... and since 250 is greater than 0, that would be the empty array.

16 个评论
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kainat rasheed
kainat rasheed 2022-5-23
@Walter Roberson so how should i actualy right. i am stuck in it
kainat rasheed
kainat rasheed 2022-5-23
@Walter Roberson see these graphs i am writing this code for it. and these are my equations. i think i am doing wrong
Walter Roberson
Walter Roberson 2022-5-23
When you call
[t,xa]=ode45(f, [0 180], [250 :0 350]);
the second [] is your initial conditions; with your code, you need three initial conditions.
I recommend that you do not use the : operator in defining your initial conditions. For example,
[t,xa]=ode45(f, [0 180], [250, 30, 350]);
but adjust that for your actual initial conditions. Do not compute them with expressions: just list them.
Torsten
Torsten 2022-5-23
编辑：Torsten 2022-5-23
Since you chose names for the constants in your code that differ from those above it is impossible for us to correct your function line
f=@(t,y) [-y(2) y(1) -A(y(1)-B); C*D*(y(3)-E) -C*y(2); -G*y(3) +F*max(0,y(1)-H)];
kainat rasheed
kainat rasheed 2022-5-23
i know i think i type it wrong as [ 2 : 0 1]
but i am having error in ode45 function . it is saying t is unused here @Walter Roberson thats is my reall problem
kainat rasheed
kainat rasheed 2022-5-23
@Walter Roberson now tell me how should i actualy write this ode 45 line in this code
Walter Roberson
Walter Roberson 2022-5-23
f=@(t,y) [-y(2) y(1) -A(y(1)-B); C*D*(y(3)-E) -C*y(2); -G*y(3) +F*max(0,y(1)-H)];
your A is a constant not a function. You cannot index A at (y(1)-B)
MATLAB is completely lacking in implied multiplication. There are no cases in MATLAB in which P(Q) means that P is to be multiplied by Q.
kainat rasheed
kainat rasheed 2022-5-26
f=@(t,y) [-y(2)y(1)-A(y(1)-B);C*D*(y(3)-E)-C*y(2);-G*y(3)+F*max(0,y(1)-H)];
@Walter Roberson what if it is like this?
Torsten
Torsten 2022-5-26
编辑：Torsten 2022-5-26
Let's play a game: search the two places where you forgot to include the "*" sign in the function definition.
kainat rasheed
kainat rasheed 2022-5-26
@Torsten i think it worked. such small change helped me alot. thankyou so so much !
kainat rasheed
kainat rasheed 2022-5-26
@Torsten i enjoyed the game. it solved my problem. thankss
Torsten
Torsten 2022-5-27
编辑：Torsten 2022-5-27
@kainat rasheed
You're welcome. I like people having humor.

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