Question

In numpy, I have a 2d array like:

[
 [1 2 3 4 5]
 [2 3 1 4 5]
 .....
 [3 5 2 3 5]
]

I want to replace each element in this array into a 1d array, e.g.

1 -> [0 0 0 0 1]
2 -> [0 0 0 1 0]

etc.

This will convert elements into arrays, and the whole 2d array into a 3d array.
I tried few things, but nothing worked. What should be the right way to do so?
Thanks.

Answer 1

Suppose this is your 2d array:

x=np.random.randint(1,3,size=(3,2))
print(x)

# [[2 2]
#  [1 2]
#  [2 1]]

Create the array:

y=np.array([[0,0,0,0,0],[0,0,0,0,1],[0,0,0,1,0]])

You can look upon this array as a mapping:

0 --> [0,0,0,0,0]   # y[0] is mapped to [0,0,0,0,0]
1 --> [0,0,0,0,1]   # y[1]      ...     [0,0,0,0,1]
2 --> [0,0,0,1,0]   # y[2]      ...     [0,0,0,1,0]

Then the array you desire is given by y[x]

print(y[x])

# [[[0 0 0 1 0]
#   [0 0 0 1 0]]

#  [[0 0 0 0 1]
#   [0 0 0 1 0]]

#  [[0 0 0 1 0]
#   [0 0 0 0 1]]]