How to find unique items and count
using unique() function we can find the unique items and their count in ndarray.
unique(ar, return_index=False, return_inverse=False, return_counts=False,
axis=None) ==> Find the unique elements of an array.
Returns the sorted unique elements of an array.
There are three optional outputs in addition to the unique elements:
- The indices of the input array that give the unique values ==> return_index.
- The indices of the unique array that reconstruct the input array.
- the number of times each unique value comes up in the input array ==>return_counts.
Example
Python
import numpy as np
help(np.unique)Output
PowerShell
Help on function unique in module numpy:
unique(ar, return_index=False, return_inverse=False, return_counts=False, axis=None)
Find the unique elements of an array.Get array with unique elements
Example
Python
a = np.array([1,1,2,3,4,2,3,4,4,1,2,3,4,5,5,6])
print(f"Original array : {a}")
print(f"Unique elements in the array using np.unique(a) : {np.unique(a)}")Output
PowerShell
Original array : [1 1 2 3 4 2 3 4 4 1 2 3 4 5 5 6]
Unique elements in the array using np.unique(a) : [1 2 3 4 5 6]Get indices also
Example
Python
a = np.array([1,1,2,3,4,2,3,4,4,1,2,3,4,5,5,6])
items,indices = np.unique(a,return_index=True)
print(f"Original array : {a}")
print(f"Unique Elements :{items}")
print(f"indices of unique elements: {indices}")Output
PowerShell
Original array : [1 1 2 3 4 2 3 4 4 1 2 3 4 5 5 6]
Unique Elements :[1 2 3 4 5 6]
indices of unique elements: [ 0 2 3 4 13 15]To get count also
Example
Python
a = np.array([1,1,2,3,4,2,3,4,4,1,2,3,4,5,5,6])
items,counts = np.unique(a,return_counts=True)
print(f"Original array : {a}")
print(f"Unique Elements :{items}")
print(f"count of unique elements: {counts}")Output
PowerShell
Original array : [1 1 2 3 4 2 3 4 4 1 2 3 4 5 5 6]
Unique Elements :[1 2 3 4 5 6]
count of unique elements: [3 3 3 4 2 1]To get all
Python
a = np.array([1,1,2,3,4,2,3,4,4,1,2,3,4,5,5,6])
items,indices,counts = np.unique(a,return_index=True,return_counts=True)
print(f"Original array : {a}")
print(f"Unique Elements :{items}")
print(f"indices of unique elements: {indices}")
print(f"count of unique elements: {counts}")Output
PowerShell
Original array : [1 1 2 3 4 2 3 4 4 1 2 3 4 5 5 6]
Unique Elements :[1 2 3 4 5 6]
indices of unique elements: [ 0 2 3 4 13 15]
count of unique elements: [3 3 3 4 2 1]Example
Python
# To get all in a program
import numpy as np
a = np.array(['a','a','b','c','a','a','b','c','a','b','d'])
items,indices,counts = np.unique(a,return_index=True,return_counts=True)
for item,index,count in zip(np.nditer(items),np.nditer(indices),np.nditer(counts)):
print(f"Element '{item}' occurred {count} times and its first occurrence
index:{index}")Output
PowerShell
Element 'a' occurred 5 times and its first occurrence index:0
Element 'b' occurred 3 times and its first occurrence index:2
Element 'c' occurred 2 times and its first occurrence index:3
Element 'd' occurred 1 times and its first occurrence index:10