Array acrobatics

Introduction to NumPy

Izzy Weber

Core Curriculum Manager, DataCamp

Data augmentation

A picture of a plastic bottle

A picture of the same plastic bottle turned upside down and mirrored

¹ Plastic bottle photo by Lilly_M via Wikimedia Commons

Flipping an array

The NumPy logo

flipped_logo = np.flip(logo_rgb_array)
plt.imshow(flipped_logo)
plt.show()

The NumPy logo after np.flip() is applied

Flipping along an axis

flipped_rows_logo = np.flip(logo_rgb_array, axis=0)
plt.imshow(flipped_rows_logo)
plt.show()

The NumPy logo with the rows of pixels in reverse order

Flipping along an axis

flipped_colors_logo = np.flip(logo_rgb_array, axis=2)
plt.imshow(flipped_colors_logo)
plt.show()

The NumPy logo with red values and blue values switched

Flipping multiple axes

flipped_except_colors_logo = np.flip(logo_rgb_array, axis=(0, 1))
plt.imshow(flipped_except_colors_logo)
plt.show()

NumPy logo with the first and second axis flipped but not the third; colors are the same as the original

Transposing an array

array = np.array([[1.1, 1.2, 1.3], 
                  [2.1, 2.2, 2.3], 
                  [3.1, 3.2, 3.3], 
                  [4.1, 4.2, 4.3]])
np.flip(array)

array([[4.3, 4.2, 4.1],
       [3.3, 3.2, 3.1],
       [2.3, 2.2, 2.1],
       [1.3, 1.2, 1.1]])

array = np.array([[1.1, 1.2, 1.3], 
                  [2.1, 2.2, 2.3], 
                  [3.1, 3.2, 3.3], 
                  [4.1, 4.2, 4.3]])
np.transpose(array)

array([[1.1, 2.1, 3.1, 4.1],
       [1.2, 2.2, 3.2, 4.2],
       [1.3, 2.3, 3.3, 4.3]])

Setting transposed axis order

transposed_logo = np.transpose(logo_rgb_array, axes=(1, 0, 2))
plt.imshow(transposed_logo)
plt.show()

Numpy logo with rows and columns transposed so that the logo appears mirrored and on its side

Let's practice!

Introduction to NumPy