CODEWITHSUNDEEP
pythonnumpy
Jeremy Harbinson
Jeremy Harbinson

Reputation: 11

create a numpy array from the minimum values in the rows of an array

Starting with a 2D Numpy array I would like to create a 1D array in which each value corresponds to the minimum value of each row in the 2D array.

For example if

dog=[[1,2],[4,3],[6,7]]

then I would like to create an array from 

'dog':[1,3,6]

This seems like it should be easy to do, but I'm not getting it so far.

Upvotes: 0

Views: 547

Answers (2)

unutbu
unutbu

Reputation: 879113

In [54]: dog=[[1,2],[4,3],[6,7]]

In [55]: np.min(dog, axis=1)
Out[55]: array([1, 3, 6])

or, if dog is a NumPy array, you could call its min method:

In [57]: dog = np.array([[1,2],[4,3],[6,7]])

In [58]: dog.min(axis=1)
Out[58]: array([1, 3, 6])

Since dog.shape is (3,2), (for 3 rows, 2 columns), the axis=1 refers to the second dimension in the shape -- the one with 2 elements. Putting axis=1 in the call to dog.min tells NumPy to take the min over the axis=1 direction, thus eliminating the axis of length 2. The result is thus of shape (3,).

Upvotes: 4

Daniel
Daniel

Reputation: 380

Without numpy:

dog=[[1,2],[4,3],[6,7]] 
mins = [min(x) for x in dog]

Upvotes: 0

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