Nonscalar arrays of function handles are not allowed; use cell arrays instead error, not sure what it means / how to fix it

%% Homework 6 544-483 
% Problem 1
clc
clear all
close all

%Parameters
global s r b 
s = 10;
r = 28;
b = 8/3;

y_int = 5;
x_int = 5;
z_int = 5;

t_init = 0;
t_final = 25;

v_init = [x_int y_int z_int];
tspan = [t_init t_final];

options = odeset('MaxStep',0.01)

%solve
[t,v] = ode45(@problem1func, tspan, v_init,options)

x = v(:,1);
y = v(:,2);
z = v(:,3);

plot(t,x,'rx')
hold on
plot(t,y,'bx')
ploy(t,z,'gx')
xlabel('t')
ylabel('pop')



%% Here's the function I am running ode 45 into

function [dvdt] = problem1func(t,v)
%v[1] = x
%v[2] = y
%v[3] = z

%dx/dt
dvdt(1) = @(x,y) -s*v(1) + s*v(2);
%dy/dt
dvdt(2) = @(x,y,z) r*v(1) - v(2) - v(1)*v(3);
%dz/dt
dvdt(3) = @(x,y,z) -b*z + x*y;
end


%Error message at the end 


Nonscalar arrays of function handles are not allowed; use cell arrays instead.

Error in problem1func (line 9)
dvdt(2) = @(x,y,z) r*v(1) - v(2) - v(1)*v(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 Problem_1 (line 26)
[t,v] = ode45(@problem1func, tspan, v_init,options)


% I've never worked with cells so this error message is confusing to me the purpose of this code is to plot the Lorenz equations. Thanks for any advice

Answer 1

[James Tursa]

You are simply using the wrong syntax for what you really want. It should be something like this instead:

%v[1] = x
%v[2] = y
%v[3] = z
dvdt = zeros(3,1);
%dx/dt
dvdt(1) = -s*v(1) + s*v(2);
%dy/dt
dvdt(2) =  r*v(1) - v(2) - v(1)*v(3);
%dz/dt
dvdt(3) =  -b*v(3) + v(1)*v(2);

[Grant Juul]

Thank you