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

Asked by Grant Juul on 11 Apr 2019
Latest activity Commented on by Grant Juul on 11 Apr 2019
%% 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

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1 Answer

Answer by James Tursa
on 11 Apr 2019
Edited by James Tursa
on 11 Apr 2019

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);