How To Convert A 1D Array Into A 2D Array?

(1) np.newaxis

Using np.newaxis will increase the dimensions of your array by one dimension when used once.
This means that a 1D array will become a 2D array, a 2D array will become a 3D array, and so on.
You can explicitly convert a 1D array with either a row vector or a column vector using np.newaxis. For example, you can convert a 1D array to a row vector by inserting an axis along the first dimension.

a = np.array([1, 2, 3, 4, 5, 6])
a

array([1, 2, 3, 4, 5, 6])

a.shape

(6,)

a2 = a[np.newaxis, :]
a2

array([[1, 2, 3, 4, 5, 6]])

a2.shape

(1, 6)

row_vector = a[np.newaxis, :]
row_vector

array([[1, 2, 3, 4, 5, 6]])

row_vector.shape

(1, 6)

col_vector = a[:, np.newaxis]
col_vector

array([[1],
       [2],
       [3],
       [4],
       [5],
       [6]])

col_vector.shape

(6, 1)

col_vector = a[:, np.newaxis][:, np.newaxis]
col_vector

array([[[1]],

       [[2]],

       [[3]],

       [[4]],

       [[5]],

       [[6]]])

col_vector.shape

(6, 1, 1)

You can also expand an array by inserting a new axis at a specified position with np.expand_dims.

a = np.array([1, 2, 3, 4, 5, 6])
a

array([1, 2, 3, 4, 5, 6])

a.shape

(6,)

b = np.expand_dims(a, axis=1)
b

array([[1],
       [2],
       [3],
       [4],
       [5],
       [6]])

b.shape

(6, 1)

c = np.expand_dims(a, axis=0)
c

array([[1, 2, 3, 4, 5, 6]])

c.shape

(1, 6)