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Numpy cbrt Example | np cbrt() Function in Python

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Numpy cbrt() is a mathematical method that is used to find the cube root of every element in a given array. To calculate cube root in Python, use the numpy cbrt() method.

Syntax

numpy.cbrt(arr1, out=None, where=True, dtype=None)

Parameters

arr1: Input array_like containing the elements whose cube root we need to find.

out : (ndarray, None, or tuple of ndarray) [Optional parameter] It defines the alternate array in which the resulting output product is to be placed. This must have the same or broadcastable shape as expected output.

where : (array_like) [Optional parameter] These are the items to be included.

dtype : [Optional parameter] It defines the type of the returned array. 

Return Value

The cube root of each of the elements in the passed array in the form of an array.

See the following figure.

numpy cbrt

 

 

Note:

  1. The cube root of complex numbers cannot be calculated using this method.
  2. If an input array is blank, then the cbrt() method returns the empty array.
  3. The cbrt() method can be used to show a parabolic plot of the cube root function.

Examples

The following example demonstrates the use of the numpy cbrt() method.

import numpy as np

arr1 = [1, 8, 27, 64]
arr2 = np.cbrt(arr1)
print(arr2)

Output

[1. 2. 3. 4.]

In this example, first, we have imported numpy and then define an array of cube elements and then use the np.cbrt() method to find the cube root of each element.

Checking for complex numbers

The following code example demonstrates the case where an array element is a complex number.

import numpy as np

arr1 = [3+4j]
arr2 = np.cbrt(arr1)
print(arr2)

Output

Traceback (most recent call last):
  File "app.py", line 4, in <module>
    arr2 = np.cbrt(arr1)
TypeError: ufunc 'cbrt' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

The interpreter throws the TypeError: ufunc ‘cbrt’ not supported for the input types, and the inputs could not safely coerced to any supported types.

Find the parabolic plot of the cube root function.

The following code example demonstrates the parabolic plot of the cube root function.

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(start=-10, stop=10, num=100, endpoint=True)

plt.title("Green : Cube root values\nOrange : Linear plot")
plt.plot(x, np.cbrt(x), color='green')

plt.plot(x, x, color='orange')
plt.show()

Output

 

Find the parabolic plot of the cube root function

Passing an empty array

The following code example demonstrates the case where an empty array is passed.

import numpy as np

arr1 = []
arr2 = np.cbrt(arr1)
print(arr2)

Output

[]

It will return an empty array.

Passing where parameter

The following code example shows the use of the where parameter to specify which elements to find the cube root of. For the remaining elements, the garbage value gets returned.

See the following code.

import numpy as np

arr1 = [1, 8, 27, 64, 125]
arr2 = np.cbrt(arr1, where=[True, False, True, False, True])
print(arr2)

Output

[1.00000000e+00 2.31584178e+77 3.00000000e+00            nan
 5.00000000e+00]

In this example, we are passing a where parameter which takes True or False values.

Specifying dtype

The following example demonstrates the case where dtype is to specify the data type of the elements.

import numpy as np

arr1 = [1, 8, 27]
arr2 = np.cbrt(arr1, dtype=np.double)
print(arr2.dtype == np.int)

arr1 = np.array([1, 8, 27], dtype=np.double)
print(np.cbrt(arr1).dtype == np.double)
print(np.cbrt(arr1).dtype == np.int)

Output

False
True
False

The following example demonstrates the application of this method in a simple programming context.

import numpy as np

n = int(input("Count: "))
numbers = []

for i in range(n):
    numbers.append(int(input()))

numbers = np.cbrt(numbers)
res = sum(numbers)

print(res)

Output

Test Case 1:
->python3 example7.py
Count: 5
1
8
27
64
125
15.0

Test Case 2:
->python3 example7.py
Count: 3
1
8
27
6.0

Conclusion

Numpy cbrt() function returns the cube-root of an array, element-wise.

In this example, we have seen how np cbrt() function works and pass the different arguments to illustrates the different output.

See also

Numpy square()

Python square

Numpy prod()

Python sqrt()

Python Modulo

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