Numpy reshape 1d to 2d array with 1 column

Question

In numpy the dimensions of the resulting array vary at run time. There is often confusion between a 1d array and a 2d array with 1 column. In one case I can ite

Answer 1

There are mainly two ways to go from 1 dimensional array (N) to 2 dimensional array with 1 column
(N x 1):

1. Indexing with np.newaxis;
2. Reshape with reshape() method.

x = np.array([1, 2, 3])  # shape: (3,) <- 1d

x[:, None]               # shape: (3, 1) <- 2d (single column matrix)
x[:, np.newaxis]         # shape: (3, 1) <- a meaningful alias to None

x.reshape(-1, 1)         # shape: (3, 1)