How to multiply matrices using a for loop

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Rachel Buckland on 17 Jan 2018
I have the equation p(t+1)=p(t)*P. p(t) is the matrix [p1(t) p2(t) p3(t) p4(t)] with p(0)=[1 0 0 0] and P is a 4x4 matrix.
I need to create a for loop that runs through the matrix multiplications until it reaches a certain p1(t). Can anyone help? Thanks.

Kaushik Lakshminarasimhan on 17 Jan 2018
p = rand(4,1); % 4x1 vector
P = rand(4,4); % 4x4 matrix
pstar = 10;
while p(1)<pstar % stop multiplying if p(1) reaches a certain pstar
p = P*p;
end
Rachel Buckland on 17 Jan 2018
I'm trying to accomplish this using a for loop do you know how to do it that way?
Kaushik Lakshminarasimhan on 18 Jan 2018
for loop is not ideal here because you do not know how many iterations you'll need a priori (unless you worked out the math). Is there a reason you insist on a for loop? If you absolutely must use it, here's one way:
p = rand(4,1); % 4x1 vector
P = rand(4,4); % 4x4 matrix
pstar = 10;
for i=1:1e4 % allow for a large enough number of iterations
p = P*p;
if p(1)>pstar, break; end
end