Error: In an assignment A(I) = B, the number of elements in B and I must be the same.

Question

LALE ASIK 2017-10-15

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评论： LALE ASIK 2017-10-16

Hello everyone. Here is the code that gives me the following error:

In an assignment A(I) = B, the number of elements in B and I must be the same.
Error in SeasonalityLVEbif>Preypred (line 33)
Ydot(1) =(alpha1*(Ke-Y(1)))+Ke*pi*Y(2)/6;

The code :

function SeasonalityLVEbif
rect=[200 80 700 650];%fix the window size and position
set(0,'defaultfigureposition',rect);
global  alpha1  b P theta q  c a e d
alpha1=0.5; b=1.2; P=0.025; theta= 0.03;q=0.0038; c= 0.81; a= 0.25; e=0.8; d=0.25;  
option=odeset('AbsTol',1e-11,'RelTol',1e-11);
inc=[0.01:1:220]';
time=[ inc ] ;
limit=[200:1:220];
ymin=[];
ymax=[];
for Ke=0.01:0.05:2,
IC=[1.5 1 0 0.5 0.25 ];
[t,U]=ode45(@Preypred,time,IC);
u1=U(limit,1);
ymin=[ymin,min(u1)];
ymax=[ymax,max(u1)];
end
X=0.01:0.05:2;
figure
plot(X, ymin,'g.',X, ymax,'k.');
legend('grazer min','grazer max'),
hold on
xlim([0.01 2]);
title('Bifurcation diagram for LVE model','FontSize',12)
xlabel('Ke, the equilibrium carrying capacity');
ylabel('grazer','Rotation',90);
function [Ydot] = Preypred(t,Y)
global alpha1 Ke b P theta q  c a e  d
Ydot(1) =(alpha1*(Ke-Y(1)))+Ke*pi*Y(2)/6;
Ydot(2) =Y(2)*(1-Y(2)^2-Y(3)^2)-2*pi*Y(3)/6;
Ydot(3) = Y(3)*(1-Y(2)^2-Y(3)^2)+2*pi*Y(2)/6;
Ydot(4) = b*Y(4)*(1-Y(4)/(min(Y(1),(P-theta*Y(5))/q)))-c*Y(4)*Y(5)/(a+Y(4));
Ydot(5) = e*min(1,((P-theta*Y(5))/Y(4))/theta)*c*Y(4)*Y(5)/(a+Y(4))-d*Y(5);
Ydot=Ydot';

Could you please help me to fix it?

1 个评论
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Stephen23 2017-10-15

编辑：Stephen23 2017-10-15

Note that you would be better off replacing the global variables with simply passing a structure of those values. Using global is almost always the worst way to pass data between workspaces.

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Answer 1

KSSV 2017-10-16

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https://ww2.mathworks.cn/matlabcentral/answers/361428-error-in-an-assignment-a-i-b-the-number-of-elements-in-b-and-i-must-be-the-same#answer_285917

在 MATLAB Online 中打开

function SeasonalityLVEbif
rect=[200 80 700 650];%fix the window size and position
set(0,'defaultfigureposition',rect);
% global  alpha1  b P theta q  c a e d
values = struct ;
values.alpha1=0.5; 
values.b=1.2; 
values.P=0.025; 
values.theta= 0.03;
values.q=0.0038; 
values.c= 0.81; 
values.a= 0.25; 
values.e=0.8; 
values.d=0.25;
option=odeset('AbsTol',1e-11,'RelTol',1e-11);
inc=[0.01:1:220]';
time=[ inc ] ;
limit=[200:1:220];
ymin=[];
ymax=[];
for Ke=0.01:0.05:2
    IC=[1.5 1 0 0.5 0.25 ];
    [t,U]=ode45(@Preypred,time,IC,[],values,Ke);
    u1=U(limit,1);
    ymin=[ymin,min(u1)];
    ymax=[ymax,max(u1)];
end
X=0.01:0.05:2;
figure
plot(X, ymin,'g.',X, ymax,'k.');
legend('grazer min','grazer max'),
hold on
xlim([0.01 2]);
title('Bifurcation diagram for LVE model','FontSize',12)
xlabel('Ke, the equilibrium carrying capacity');
ylabel('grazer','Rotation',90);
function [Ydot] = Preypred(t,Y,values,Ke)
Ydot = zeros(1,5) ;
alpha1 = values.alpha1 ;
b = values.b ; 
P = values.P ; 
theta = values.theta ;
q = values.q ;
c = values.c ;
a = values.a ;
e = values.e ; 
d = values.d ;
Ydot(1) =(alpha1*(Ke-Y(1)))+Ke*pi*Y(2)/6;
Ydot(2) =Y(2)*(1-Y(2)^2-Y(3)^2)-2*pi*Y(3)/6;
Ydot(3) = Y(3)*(1-Y(2)^2-Y(3)^2)+2*pi*Y(2)/6;
Ydot(4) = b*Y(4)*(1-Y(4)/(min(Y(1),(P-theta*Y(5))/q)))-c*Y(4)*Y(5)/(a+Y(4));
Ydot(5) = e*min(1,((P-theta*Y(5))/Y(4))/theta)*c*Y(4)*Y(5)/(a+Y(4))-d*Y(5);
Ydot=Ydot';