# How do I plot a function which depends on a changing variable?

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Rowan Miller on 4 Dec 2017
Answered: Jim Hokanson on 5 Dec 2017
So I have to plot the movement of a spring once let go for -2<t<20 given yo=5(distance the spring is stretched initially), w=5(angular frequency), k=0.1/s. It has to be done using a for loop and if statements.
I am new to matlab so I don't know what to do from here. Thank you.
Here's the code I have:
t = -2;
yo = 5;
w = 5;
k = 0.1;
for t = -2:20
if t < 0
y = -yo;
elseif t < 10
y = -yo*(cos(w*t));
else
y = -yo*(cos(w*t))*exp(-k*(t-10));
end
t = t + 0.1;
end

Jim Hokanson on 5 Dec 2017
You could use something like animatedline if you want to calculate a single point and add it to a graph. If you want to use a loop the more typical approach is to initialize t and y, then loop over t and update y.
t_all = -2:0.1:20;
y = zeros(1,length(t_all));
for i = 1:length(t_all)
t = t_all(i);
y(i) = ...
end
plot(t_all,y)

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