The command
N = randn(1440,1000);
will generate 1000 datasets comprising 1440 Gaussian random numbers and store them as columns of the matrix N.
Then
plot(N)
will result in a huge mess on the current axes :).
Then, try
max(N)
to get the maximum value for each of the 1000 datasets, or try
max(N(:))
to get the maximum of all 1440000 random numbers.
