hi, what does ~ mean in the following code

 [t02,~] = ode23(@(t,x)system.deriv(t,x,0, xd, @(t)lookup_u(zdot,t)), [0 2], init.fun(xd),opt);

Answer 1

[Image Analyst]

It means to ignore that output. Don't take the second output and assign it to any variable - just ignore it completely, throw it away. You could also just do

t02 = ode23(.............

Since the ignored output is the later one. You can't do that if you want to ignore the first one and keep the second one though.

[Muna Shehan]

Thanks for your response

[Guillaume]

Note that for ode23

[t02, ~] = ode23(...

and

t02 = ode23(...

are equivalent. This is not the case with all functions, e.g.

   idx = find(...
   [row, ~] = find(...

The first find returns a linear index. The second, a row and column where you ignore the column.