# How to find the number of occurrence of matrix element with numpy in python ?

Examples of how to find the number of occurrence of a given element in a matrix with numpy in python ?

### Create a random matrix with numpy

Let's create a random matrix of size (4,4) with random integers between 0 and 4:

````import numpy as np`

`A = np.random.randint(0,5,(4,4))`
```

returns for example

````[[3 0 2 2]`
` [1 3 4 2]`
` [0 0 3 1]`
` [2 3 3 1]]`
```

### Find the number of occurrences for each item

To find the number of occurrences for each element one solution is to use the numpy function "unique":

````unique, counts = np.unique(A, return_counts=True)`

`for i in range(len(unique)):`
`    print(unique[i],counts[i])`
```

returns

````0 3`
`1 3`
`2 4`
`3 5`
`4 1`
```

It is then possible to create a dictionary

````dict(zip(unique, counts))`
```

returns

````{0: 3, 1: 3, 2: 4, 3: 5, 4: 1}`
```

### Find the number of occurrences for a given element using where

Another solution to find the occurrence number of 3 using where:

````np.where(A==3).shape`
```

returns

````5`
```

### Find the number of occurrences for a given element using the collections module

Another example of how to find the number of occurrences of a given element in an array

````import collections`

`collections.Counter(A.ravel())`
```

returns

````Counter({3: 5, 0: 3, 2: 4, 1: 3, 4: 1})`
```