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Index exceeds the number of array elements. Index must not exceed 3. HELP

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Elizabeth Pickford
Elizabeth Pickford 2024-4-26
回答： Sam Chak 2024-4-26
model code:
clear all;
close all;
S = 99;
I = 1;
R = 0;
N = 100; %Total population
beta= 0.1; % birth rate
alpha= 0.1; % infection person to person rate
lambda= 0.3; % infection by water rate
vac= 0.05; % recovery by vaccination rate
d= 0.03; % death rate
gamma= 0.8; % recovery rate
c= 0.9; % rate of contamination
m= 0.4; % rate of decay of V. cholerae
B= 0.0; % initial concentration of V. cholerae
t_f = 500; %Ending time of simulation
Q = [beta alpha lambda vac d gamma c m B];
[t,y]=ode45('cholera_de',[0:t_f/100:t_f],[S I R]',[],Q);
figure(1)
plot(t,y(:,1),'k-',t,y(:,2),'r--',t,y(:,3),'b:');
xlabel('\bf Time (days)');
ylabel('\bf Number of People by Category');
legend('S','I','R');
z=y(end,:)'
SN=y(:,1)/N;
IN=y(:,2)/N;
figure(2)
plot(IN,SN);
xlabel('\bf I/N');
ylabel('\bf S/N');
r0=beta/beta
[maxIN,y_maxtime]=max(y(:,2)/N);
maxIN
maxtime=y(y_maxtime)
eqIN=y(100,2)/N;
eqIN
function code:
function dy=cholera_de(t,Y,flag,Q)
beta= Q(1);
alpha= Q(2);
lambda= Q(3);
vac= Q(4);
d= Q(5);
gamma= Q(6);
c= Q(7);
m= Q(8);
S= Y(1);
I= Y(2);
R= Y(3);
B=Y(4);
N= S+I+R;
dy(1,1)= beta - alpha*I - lambda*B - vac*S - d;
dy(2,1)= alpha*I + lambda*B - d - gamma*I;
dy(3,1)= gamma*I + vac*S - d;
dy(4,1)= c*I - m*B;
Gives me this error:
Index exceeds the number of array elements. Index must not exceed 3.
Error in cholera_de (line 15)
B=Y(4);
Error in odearguments (line 92)
f0 = ode(t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Error in ode45 (line 104)
odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
Error in cholera_model (line 23)
[t,y]=ode45('cholera_de',[0:t_f/100:t_f],[S I R]',[],Q);
  1 个评论
Chuguang Pan
Chuguang Pan 2024-4-26
编辑：Chuguang Pan 2024-4-26
It seems that your initial condition is [S I R]', which has three elements. However, the cholera_de function need four states Y(1), Y(2), Y(3), Y(4). You should keep number of initial states the same as states transfered to cholera_de function.

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回答（1 个）

Sam Chak
Sam Chak 2024-4-26
Ran in:
Hi @Elizabeth Pickford
Few places require fixes. Check out the annotated lines.
S0 = 99;
I0 = 1;
R0 = 0;
N0 = S0 + I0 + R0; % Total population % <-- fix it here
beta = 0.1; % birth rate
alpha = 0.1; % infection person to person rate
lambda = 0.3; % infection by water rate
vac = 0.05; % recovery by vaccination rate
d = 0.03; % death rate
gamma = 0.8; % recovery rate
c = 0.9; % rate of contamination
m = 0.4; % rate of decay of V. cholerae
B = 0.0; % initial concentration of V. cholerae
Q = [beta alpha lambda vac d gamma c m B];
t_f = 500; % Ending time of simulation
tspan = [0:t_f/100:t_f]; % <-- fix it here
y0 = [S0; I0; R0; N0]; % <-- fix it here
[t, y] = ode45(@(t, y) cholera_de(t, y, Q), tspan, y0); % <-- fix it here
figure(1)
plot(t,y(:,1),'k-',t,y(:,2),'r--',t,y(:,3),'b:'); grid on
xlabel('\bf Time (days)');
ylabel('\bf Number of People by Category');
legend('S', 'I', 'R');
z = y(end,:)'
z = 4x1
14.2061 -0.9011 91.6949 -2.0108
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
N = y(:,1) + y(:,2) + y(:,3); % <-- fix it here
SN = y(:,1)./N; % <-- fix it here
IN = y(:,2)./N; % <-- fix it here
figure(2)
plot(IN, SN); grid on
xlabel('\bf I/N');
ylabel('\bf S/N');
r0 = beta/beta;
[maxIN, y_maxtime] = max(y(:,2)/N);
maxIN;
maxtime = y(y_maxtime);
eqIN = y(100,2)/N;
eqIN;
function dy = cholera_de(t, y, Q) % <-- fix it here
%% parameters
beta = Q(1);
alpha = Q(2);
lambda = Q(3);
vac = Q(4);
d = Q(5);
gamma = Q(6);
c = Q(7);
m = Q(8);
%% definitions
S = y(1);
I = y(2);
R = y(3);
B = y(4);
N = S + I + R;
%% differential equations
dy(1,1) = beta - alpha*I - lambda*B - vac*S - d;
dy(2,1) = alpha*I + lambda*B - gamma*I - d;
dy(3,1) = gamma*I + vac*S - d;
dy(4,1) = c*I - m*B;
end

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