Compute the differences between consecutive elements and prepend & append array of numbers in Numpy

To compute the differences between consecutive elements of a masked array, use the MaskedArray.ediff1d() method in Python Numpy.

The "to_begin" parameter sets the array of number(s) to prepend at the start of the returned differences. The "to_end" parameter sets the array of number(s) to append at the end of the returned differences.

A masked array is the combination of a standard numpy.ndarray and a mask. A mask is either nomask, indicating that no value of the associated array is invalid, or an array of booleans that determines for each element of the associated array whether the value is valid or not.

Steps

At first, import the required library −

import numpy as np
import numpy.ma as ma

Create an array with int elements using the numpy.array() method −

arr = np.array([[65, 68, 81], [93, 33, 76], [73, 88, 51], [62, 45, 67]])
print("Array...
", arr)

Create a masked array and mask some of them as invalid −

maskArr = ma.masked_array(arr, mask =[[1, 0, 0], [ 0, 0, 0], [0, 1, 0], [0, 0, 0]])
print("\nOur Masked Array...
", maskArr)

Get the type of the masked array −

print("\nOur Masked Array type...
", maskArr.dtype)

Get the dimensions of the Masked Array −

print("\nOur Masked Array Dimensions...
",maskArr.ndim)

Get the shape of the Masked Array −

print("\nOur Masked Array Shape...
",maskArr.shape)

Get the number of elements of the Masked Array −

print("\nNumber of elements in the Masked Array...
",maskArr.size)

To compute the differences between consecutive elements of a masked array, use the MaskedArray.ediff1d() −

prepArr = np.array([-4, -3, -2, -1])
appeArr = np.array([997, 998, 999])
print("\nResult..
.", np.ediff1d(maskArr, to_begin = prepArr, to_end=appeArr))

Example

# Python ma.MaskedArray - Compute the differences between consecutive elements
# and prepend & append array of numbers

import numpy as np
import numpy.ma as ma

# Create an array with int elements using the numpy.array() method
arr = np.array([[65, 68, 81], [93, 33, 76], [73, 88, 51], [62, 45, 67]])
print("Array...
", arr)

# Create a masked array and mask some of them as invalid
maskArr = ma.masked_array(arr, mask =[[1, 0, 0], [ 0, 0, 0], [0, 1, 0], [0, 0, 0]])
print("\nOur Masked Array...
", maskArr)

# Get the type of the masked array
print("\nOur Masked Array type...
", maskArr.dtype)
# Get the dimensions of the Masked Array
print("\nOur Masked Array Dimensions...
",maskArr.ndim)

# Get the shape of the Masked Array
print("\nOur Masked Array Shape...
",maskArr.shape)

# Get the number of elements of the Masked Array
print("\nNumber of elements in the Masked Array...
",maskArr.size)

# To compute the differences between consecutive elements of a masked array, use the MaskedArray.ediff1d() method in Python Numpy
# The "to_begin" parameter sets the array of number(s) to prepend at the start of the returned differences.
# The "to_end" parameter sets the array of number(s) to append at theend of the returned differences.
prepArr = np.array([-4, -3, -2, -1])
appeArr = np.array([997, 998, 999])
print("\nResult..
.", np.ediff1d(maskArr, to_begin = prepArr, to_end=appeArr))

Output

Array...
[[65 68 81]
[93 33 76]
[73 88 51]
[62 45 67]]

Our Masked Array...
[[-- 68 81]
[93 33 76]
[73 -- 51]
[62 45 67]]

Our Masked Array type...
int64

Our Masked Array Dimensions...
2

Our Masked Array Shape...
(4, 3)

Number of elements in the Masked Array...
12
Result..
[ -4 -3 -2 -1 3 13 12 -60 43 -3 15 -37 11 -17 22 997 998 999]