reshape to 2d array numpy code example

Example 1: numpy convert 1d array to 2d

import numpy as np 

# 1D array 
one_dim_arr = np.array([1, 2, 3, 4, 5, 6])

# to convert to 2D array
# we can use the np.ndarray.reshape(shape) function 
# here shape is given by two integers seperated by a comma
# the two integers specify m,n for the new matrix 
# ensure that the matrix that you are trying to generate
# has a size that meets the number of elements in the 1D array. 
# for that make sure that 
# m * n = number of elements in the one dimentional array 

two_dim_arr = one_dim_arr.reshape(1, 6)

#which returns a 2D array
print(two_dim_arr)


# confirmed by the array.ndim attribute
print(two_dim_arr.ndim)

# you can even specify one of the dimensions as unknown by passing -1
# numpy will infer the length using the array and remaining dimensions

two_dim_arr = one_dim_arr.reshape(1,-1)

Example 2: convert np shape (a,) to (a,1)

# numpy array/vector (n,) dimension -> (n,1) dimension conversion
a  = np.arange(3)         # a.shape  = (3,)
b  = a.reshape((3,1))     # b.shape  = (3,1)
c  = b.reshape((3,))      # c.shape  = (3,)

c2 = b.reshape((-1,1))    # c2.shape = (3,)