rand(method,s) causes rand to use the generator determined by method, and initializes the state of that generator using the value of s.
The value of s is dependent upon which method is selected. If method is set to 'state' or 'twister', then s must be either a scalar integer value from 0 to 2^32-1 or the output of rand(method). If method is set to 'seed', then s must be either a scalar integer value from 0 to 2^31-2 or the output of rand(method).
Input argument method can be any of the strings shown in the table below:
'state'
Use a modified version of Marsaglia's subtract with borrow algorithm (the default in MATLAB versions 5 and later). This method can generate all the double-precision values in the closed interval [2^(-53), 1-2^(-53)]. It theoretically can generate over 2^1492 values before repeating itself.
'seed'
Use a multiplicative congruential algorithm (the default in MATLAB version 4). This method generates double-precision values in the closed interval [1/(2^31-1), 1-1/(2^31-1)], with a period of 2^31-2.
'twister'
Use the Mersenne Twister algorithm by Nishimura and Matsumoto. This method generates double-precision values in the closed interval [2^(-53), 1-2^(-53)], with a period of (2^19937-1)/2.
那个参数seed并不是用来定义随机数的初始值的，而只是作为选择随机数产生器的选项，如果使用了seed参数，就选择了某种算法（也就是随机数产生器）产生随机数。
rand只能产生0-1之间的随机数，要产生其它范围的随机数据可以用一个数与rand相乘即可！
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