NumPy Summations
Summations
What is the difference between summation and addition?
Addition is done between two arguments whereas summation happens over n elements.
Example
Add the values in arr1 to the values in arr2:
import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.add(arr1, arr2)
print(newarr)
Try it Yourself »arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.add(arr1, arr2)
print(newarr)
Returns:[2 4 6]
Example
Sum the values in arr1 and the values in arr2:
import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.sum([arr1, arr2])
print(newarr)
Try it Yourself »arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.sum([arr1, arr2])
print(newarr)
Returns:12
Summation Over an Axis
If you specifyaxis=1, NumPy will sum the numbers in each array.
Example
Perform summation in the following array over 1st axis:
import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.sum([arr1, arr2], axis=1)
print(newarr)
Try it Yourself »arr1 = np.array([1, 2, 3])
arr2 = np.array([1, 2, 3])
newarr = np.sum([arr1, arr2], axis=1)
print(newarr)
Returns:[6 6]
Cummulative Sum
Cummulative sum means partially adding the elements in array.
E.g. The partial sum of [1, 2, 3, 4] would be [1, 1+2, 1+2+3, 1+2+3+4] = [1, 3, 6, 10].
Perfom partial sum with thecumsum() function.
Example
Perform cummulative summation in the following array:
import numpy as np
arr = np.array([1, 2, 3])
newarr = np.cumsum(arr)
print(newarr)
Try it Yourself »arr = np.array([1, 2, 3])
newarr = np.cumsum(arr)
print(newarr)
Returns:[1 3 6]
