hi, what does ~ mean in the following code

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Muna Shehan
Muna Shehan 2014-9-1
评论： Guillaume 2014-9-1
[t02,~] = ode23(@(t,x)system.deriv(t,x,0, xd, @(t)lookup_u(zdot,t)), [0 2], init.fun(xd),opt);

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Image Analyst
Image Analyst 2014-9-1
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.
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Guillaume
Guillaume 2014-9-1
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.

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