Error using vertcat Dimensions of arrays being concatenated are not consistent.

Hello. When I start the program, I get an error about using vertcat, I don’t understand why, I tried to find information and fix it, but apparently I’m missing something. What can I do to solve the problem?

function f=M86()

n = 1;b=1; k = -4; a = 1; h = 3; p = (1/4)*pi; y(1)=0;y(2)=1;x=2;
f=[y(2);y(2)+2.*n.*(1+a.*y.^3).*y(1)+k.^2.*(y(1)+b.*y(1).^3)-h.*sin(p.*x)];

clc
disp('Значения параметров: n = 1,b=2, k = -4, a = 1, h = 3,b =2, p = (1/4)*Pi')
disp('Решение задачи Коши для уравнения')
[~,y] = ode45('f',[0,1],[0,0],1,2,-4,1,3,2,(1./4).*pi);
plot(y(:,1),y(:,2))
tic,[~,~]=ode45('M86',[-1,1],[0,0],1,2,-4,1,3,2,(1./4).*pi);toc
grid on
end

[Dyuman Joshi]

y(2) is a single element i.e 1x1. Whereas, the second row in the definition of f is 1x2.

You can not vertically concatenate 1x1 with a 1x2.

What is the ODE that you are trying to solve? Can you share the mathematical expression?

n = 1;b=1; k = -4; a = 1; h = 3; p = (1/4)*pi; 
y(1)=0;y(2)=1;x=2;

y(2)

ans = 1

y(2)+2.*n.*(1+a.*y.^3).*y(1)+k.^2.*(y(1)+b.*y(1).^3)-h.*sin(p.*x)

ans = 1×2

-2 -2

[Walter Roberson]

Note by the way that using a character vector (or string scalar) as the name of the ode function is recommended against. You should use a function handle instead.

When you use a character vector (or string scalar) then the function named must have its own .m file (or be a .mdl or .slx or .p). In particular, it cannot be the name of a function that is in the same file as the ode45* call.

[Walter Roberson]

disp('Значения параметров: n = 1,b=2, k = -4, a = 1, h = 3,b =2, p = (1/4)*Pi')

Значения параметров: n = 1,b=2, k = -4, a = 1, h = 3,b =2, p = (1/4)*Pi

disp('Решение задачи Коши для уравнения')

Решение задачи Коши для уравнения

[~,y] = ode45(@f,[0,1],[0,0],1,2,-4,1,3,2,(1./4).*pi);

Unrecognized function or variable 'f'.

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);

plot(y(:,1),y(:,2))
tic,[~,~]=ode45(@M86,[-1,1],[0,0],1,2,-4,1,3,2,(1./4).*pi);toc
grid on

function f=M86()

n = 1;b=1; k = -4; a = 1; h = 3; p = (1/4)*pi; y(1)=0;y(2)=1;x=2;
f=[y(2);y(2)+2.*n.*(1+a.*y.^3).*y(1)+k.^2.*(y(1)+b.*y(1).^3)-h.*sin(p.*x)];
end

Answer 1

[Torsten]

Maybe you mean something like this.

I don't know whether it must read y(1) or y(2) at the place marked in bold letter in the next line ; I assumed y should be y(1).

f=@(t,y)[y(2);y(2)+2.*n.*(1+a.*y.^3).*y(1)+k.^2.*(y(1)+b.*y(1).^3)-h.*sin(p.*x)];

M86()

Значения параметров: n = 1,b=1, k = -4, a = 1, h = 3, p = (1/4)*Pi
Решение задачи Коши для уравнения

function M86
  n = 1;b=1; k = -4; a = 1; h = 3; p = (1/4)*pi; y(1)=0;y(2)=1;x=2;
  f=@(t,y)[y(2);y(2)+2.*n.*(1+a.*y(1).^3).*y(1)+k.^2.*(y(1)+b.*y(1).^3)-h.*sin(p.*x)];
  disp('Значения параметров: n = 1,b=1, k = -4, a = 1, h = 3, p = (1/4)*Pi')
  disp('Решение задачи Коши для уравнения')
  [~,y] = ode45(f,[0,1],[0,0]);
  plot(y(:,1),y(:,2))
end