Error in simple ode45 functions

Hello, I am trying to solve a non-stiff 2nd order ODE with ode45 function. My ODE is d^2y/dt^2 = -g + (4/15)*(1/m)*(dy/dt)^2

Here is the ode function file that I made

function [ ode_fun_vect ] = ode_1_fun( t,z )
global m g
m=80;
g=9.81;
ode_fun_vec=[z(1);-g+(4/15)*(z(1))^2/m];

end

And here is script to solve ode:

clc;
clear all;
close all;

initial_cond=[600,0];
time_range=[0,20];

[t,y]=ode45(@ode_1_fun,time_range,initial_cond);

figure();

subplot(2,1,1);
plot(t,y(:,1));
xlabel('time');
ylabel('displacement');

subplot(2,1,2);
plot(t,y(:,2));
xlabel('time');
ylabel('velocity');

However I am getting some errors saying: Output argument "ode_fun_vect" (and maybe others) not assigned during call

Can someone help me? Thanks in advance!

Answer 1

[Star Strider]

Typo!

You defined ‘ode_fun_vect’ as your function output and ‘ode_fun_vec’ as the value it calculates. Change one or the other and your ODE integrates successfully.

[Amit Kumar]

haha, so silly mistake of mine! Thanks a lot!!

[Star Strider]

My pleasure!

That’s the first problem I look for, since I have typos in my own code more often than I’d like to admit.