How to output a value of an array for a specific value of time?

I have the following section of code. I am generating arrays of t and v to create a plot.

wn and theta are given.

n=3; N=500; t=linspace(0,n*Tn,N); v=rho*cos(wn*t+theta);

Now how do I print the value of v for t=1?

Answer 1

[David Sanchez]

idx = find(t==1);
v(idx)

or in a single line:

v( find(t==1) )

[David Sanchez]

or just

v( t==1 )

[Abhinav Prashant Mohanakrishnan]

What happens if 1 is not a part of the array 't'?

[David Sanchez]

you will get an empty matrix

>> v(t==1)

ans =

     Empty matrix: 1-by-0

[Abhinav Prashant Mohanakrishnan]

That's exactly my problem. I generated 't' to plot a displacement vs time graph but I also need the displacement value at time t. So now that 't' is an empty vector, I am not able to print anything. Is there a way to goal seek using linspace? Somehow include 1 in the series?

[David Sanchez]

Absolutely, as explained by Daniel in http://www.mathworks.com/matlabcentral/answers/48942-insert-element-in-vector you can do this:

t=linspace(0,n*Tn,N);

idx = find(t<1,1);
insert = @(a, x, n)cat(2,  x(1:n), a, x(n+1:end)); % function to insert the value "a" in array "x" in position "n"
t = insert(1, t, idx); % now t contains the value "1"

v=rho*cos(wn*t+theta);