Rand随机数
 

 rand Uniformly distributed pseudorandom numbers.
    R = rand(N) returns an N-by-N matrix containing pseudorandom values drawn
    from the standard uniform distribution on the open interval(0,1).  rand(M,N)
    or rand([M,N]) returns an M-by-N matrix.  rand(M,N,P,...) or
    rand([M,N,P,...]) returns an M-by-N-by-P-by-... array. 
R=rand（N）返回一个N*N阶矩阵，R=rand(M*N)返回一个M*N阶的矩阵，同理可以返回一个M*N*P*Q。。。阶的矩阵，但是矩阵中的每一个元素都是取值于（0,1）的随机数
rand returns a
    scalar.  rand(SIZE(A)) returns an array the same size as A.
 
    Note: The size inputs M, N, P, ... should be nonnegative integers.
    Negative integers are treated as 0.
 
    R = rand(..., 'double') or R = rand(..., 'single') returns an array of
    uniform values of the specified class.
 
    Compatibility Note: In versions of MATLAB prior to 7.7, you controlled
    the internal state of the random number stream used by rand by calling
    rand directly with the 'seed', 'state', or 'twister' keywords.  That
    syntax is still supported for backwards compatibility, but is deprecated.
    Beginning in MATLAB 7.7, use the default stream as described in
    RANDSTREAM.
 
    The sequence of numbers produced by rand is determined by the internal
    state of the uniform pseudorandom number generator that underlies rand,
    RANDI, and RANDN.  Control that default random number stream using its
    properties and methods.  See RANDSTREAM for details about the default
    stream.
 
    Resetting the default stream to the same fixed state allows computations
    to be repeated.  Setting the stream to different states leads to unique
    computations, however, it does not improve any statistical properties.
    Since MATLAB uses the same state each time it starts up, rand, RANDN, and
    RANDI will generate the same sequence of numbers in each session unless
    the state is changed.
 
    Examples:
 
       Generate values from the uniform distribution on the interval [a, b].
          r = a + (b-a).*rand(100,1);
 
       Generate integer values from the uniform distribution on the set 1:n.
          r = randi(100,1);
 
       Save the current state of the default stream, generate 5 values,
       restore the state, and repeat the sequence.
          defaultStream = RandStream.getDefaultStream;
          savedState = defaultStream.State;
          u1 = rand(1,5)
          defaultStream.State = savedState;
          u2 = rand(1,5) % contains exactly the same values as u1
 
       Replace the default stream with a stream whose seed is based on CLOCK, so
       rand will return different values in different MATLAB sessions.  NOTE: It
       is usually not desirable to do this more than once per MATLAB session.
          RandStream.setDefaultStream(RandStream('mt19937ar','seed',sum(100*clock)));
          rand(1,5)