You can accomplish this using the "randperm" function. For example, to get 264 numbers between 1 and 284, you could use the following code:
>> idx = randperm(284, 264);
If the variable "M" is storing your data, you can then get the rows specified in "idx" with the following code:
>> M_subset = M(idx, :);
For more information on "randperm", please refer to the following documentation link:
