Building an array in python
Suppose we have an array of length 1000
, where are all its values 1
, that is, this is how [1,1,1,1,1,1,…,1,1,1,1]
. Now suppose that we want to convert this array into an array of blocks so that the 25%
array was a unit 0
instead 1
arranged uniformly at random positions . Hence the final array would be something like [1,1,1,1,1,1,1,0,0,0,1,1,1,1,1,0,0,0,…,1,1,1,0,0,0]
.
Is there an efficient way for python / numpy?
You can create a list of random indices with the length of the main list 0.25
and then change that the indices in the main list are 0.
>>> l=np.ones(30)
>>> length=len(l)
>>> rand=np.arange(int(0.25*length))
>>> np.random.shuffle(rand)
>>> l[rand]=0
>>> l
array([0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1,
0, 0, 1, 1, 1, 0, 1])
And more precisely, you can do:
main_list[np.random.choice(length,int(0.25*length),replace=False)]=0
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