Python Numpy vstack() Method with Examples

Numpy.vstack() Method in Python:

Numpy.vstack() is a Python function that concatenates a tuple of arrays vertically along the first dimension to create a single array.

To build a single array, it stacks the sequence of input arrays vertically.

Syntax:

numpy.vstack(tuple)

Parameters

tuple: It is the sequence of ndarrays that we want to concatenate. Except for the first axis, the arrays must have the same shape along all axis.

Return Value:

It returns a stacked ndarray i.e, the stacked array of the input arrays.

Numpy vstack() Method with Examples in Python

Example1

Approach:

Import numpy module using the import keyword.
Give the first array as static input using the array() function and store it in a variable.
Give the second array as static input using the array() function and store it in another variable.
Give the third array as static input using the array() function and store it in another variable.
Print the dimensions/shape of the above given 3 arrays using the shape function.
Pass the above given 3 arrays as arguments to the vstack() function to get a vertically stacked 2-D array.
Store it in another variable.
Print the shape of the above stack array using the shape function.
The Exit of the Program.

Below is the implementation:

# Import numpy module using the import keyword
import numpy
# Give the first array as static input using the array() function
# and store it in a variable
gvn_arry1= numpy.array([4, 6, 1, 9])
# Give the second array as static input using the array() function and
# store it in another variable
gvn_arry2 = numpy.array([2, 3, 1, 14])
# Give the third array as static input using the array() function and 
# store it in another variable
gvn_arry3 = numpy.array([8, 5, 4, 9])
# Print the dimensions/shape of the above given 3 arrays using the shape function
print("Given First array shape is:", gvn_arry1.shape)
print("Given second array shape is:", gvn_arry2.shape)
print("Given third array shape is:", gvn_arry3.shape)
print()
# Pass the above given 3 arrays as arguments to the vstack() function
# to get a vertically stacked 2-D array.
# store it in another variable
stack_arry = numpy.vstack((gvn_arry1, gvn_arry2, gvn_arry3))
print("The Stacked array for the above given 3 arrays is:")
print(stack_arry)
# Print the shape of the above stack array using the shape function
print("The result stacked array shape is:", stack_arry.shape)

Output:

Given First array shape is: (4,)
Given second array shape is: (4,)
Given third array shape is: (4,)

The Stacked array for the above given 3 arrays is:
[[ 4 6 1 9]
 [ 2 3 1 14]
 [ 8 5 4  9]]
The result stacked array shape is: (3, 4)

Example2: The arrays are stacked along the first dimensions for N-Dimensional arrays

# Import numpy module using the import keyword
import numpy
# Give the first array(2D) as static input using the array() function
# and store it in a variable
gvn_arry1= numpy.array([ [10, 5, 1], [2, 7, 3] ])
# Give the second array(2D) as static input using the array() function and
# store it in another variable
gvn_arry2 = numpy.array([ [4, 1, 6], [1, 8, 9] ])
# Print the dimensions/shape of the above given two 2D arrays using the shape function
print("Given First array shape is:", gvn_arry1.shape)
print("Given second array shape is:", gvn_arry2.shape)
print()
# Pass the above given 2 arrays as arguments to the vstack() function
# to get a vertically stacked array.
# store it in another variable
stack_arry = numpy.vstack((gvn_arry1, gvn_arry2))
print("The Stacked array for the above given two 2D arrays is:")
print(stack_arry)
# Print the shape of the above stack array using the shape function
print("The result stacked array shape is:", stack_arry.shape)

Output:

Given First array shape is: (2, 3)
Given second array shape is: (2, 3)

The Stacked array for the above given two 2D arrays is:
[[10 5 1]
 [ 2 7 3]
 [ 4 1 6]
 [ 1 8 9]]
The result stacked array shape is: (4, 3)

The shape of N-dimensional arrays must be the same along all dimensions except the first, as seen below:

Example3

# Import numpy module using the import keyword
import numpy
# Give the first array as static input using the array() function
# and store it in a variable
gvn_arry1= numpy.array([ [10, 5], [2, 7] ])
# Give the second array as static input using the array() function and
# store it in another variable
gvn_arry2 = numpy.array([ [4, 1], [1, 9], [6, 5]])
# Print the dimensions/shape of the above given two arrays using the shape function
print("Given First array shape is:", gvn_arry1.shape)
print("Given second array shape is:", gvn_arry2.shape)
print()
# Pass the above given 2 arrays as arguments to the vstack() function
# to get a vertically stacked array.
# store it in another variable
stack_arry = numpy.vstack((gvn_arry1, gvn_arry2))
print("The Stacked array for the above given two arrays is:")
print(stack_arry)
# Print the shape of the above stack array using the shape function
print("The result stacked array shape is:", stack_arry.shape)

Output:

Given First array shape is: (2, 2)
Given second array shape is: (3, 2)

The Stacked array for the above given two arrays is:
[[10 5]
 [ 2 7]
 [ 4 1]
 [ 1 9]
 [ 6 5]]
The result stacked array shape is: (5, 2)

Numpy vstack() Method with Examples in Python

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