ipython - The random number generator in numpy -

i using numpy.random.randnand numpy.random.randto generate random numbers. confusing difference between random.randn , random.rand?

the main difference between 2 mentioned in docs. links doc rand , doc randn

for numpy.rand, random values generated uniform distribution within 0 - 1

but numpy.randn random values generated normal distribution, with mean 0 , variance 1.

just small example.

>>> import numpy np >>> np.random.rand(10) array([ 0.63067838,  0.61371053,  0.62025104,  0.42751699,  0.22862483,         0.75287427,  0.90339087,  0.06643259,  0.17352284,  0.58213108]) >>> np.random.randn(10) array([ 0.19972981, -0.35193746, -0.62164336,  2.22596365,  0.88984545,        -0.28463902,  1.00123501,  1.76429108, -2.5511792 ,  0.09671888]) >>>  

as can see rand gives me values within 0-1,

whereas randn gives me values mean == 0 , variance == 1

to explain further, let me generate large enough sample:

>>> = np.random.rand(100) >>> b = np.random.randn(100) >>> np.mean(a) 0.50570149531258946 >>> np.mean(b) -0.010864958465191673 >>> 

you can see mean of a close 0.50, generated using rand. mean of b on other hand close 0.0, generated using randn