# \$1log10
<a name="log10"></a>

New from version 4.0.

The `$log10` operator in Amazon DocumentDB is used to calculate the base-10 logarithm of a number. It is useful for performing logarithmic calculations on numeric fields within the aggregation pipeline.

**Parameters**
+ `expression`: The numeric expression for which the base-10 logarithm is to be calculated.

## Example (MongoDB Shell)
<a name="log10-examples"></a>

The following example demonstrates how to use the `$log10` operator to calculate the base-10 logarithm of a numeric field.

**Create sample documents**

```
db.numbers.insertMany([
  { _id: 1, value: 1 },
  { _id: 2, value: 10 },
  { _id: 3, value: 100 },
  { _id: 4, value: 1000 }
]);
```

**Query example**

```
db.numbers.aggregate([
  {
    $project: {
      _id: 1,
      log10Value: { $log10: "$value" }
    }
  }
]);
```

**Output**

```
[
  { "_id": 1, "log10Value": 0 },
  { "_id": 2, "log10Value": 1 },
  { "_id": 3, "log10Value": 2 },
  { "_id": 4, "log10Value": 3 }
]
```

## Code examples
<a name="log10-code"></a>

To view a code example for using the `$log10` command, choose the tab for the language that you want to use:

------
#### [ Node.js ]

```
const { MongoClient } = require('mongodb');

async function example() {
  let client;

  try {
    client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
    
    const db = client.db('test');
    const collection = db.collection('numbers');

    const result = await collection.aggregate([
      {
        $project: {
          _id: 1,
          log10Value: { $log10: "$value" }
        }
      }
    ]).toArray();

    console.log(result);
  } catch (error) {
    console.error("An error occurred:", error);
  } finally {
    if (client) {
      await client.close();
    }
  }
}

example();
```

------
#### [ Python ]

```
from pymongo import MongoClient

def example():
    client = None
    try:
        client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
        
        db = client.test
        collection = db.numbers

        result = list(collection.aggregate([
            {
                '$project': {
                    '_id': 1,
                    'log10Value': { '$log10': '$value' }
                }
            }
        ]))

        print(result)
    
    except Exception as e:
        print(f"An error occurred: {e}")
    
    finally:
        if client:
            client.close()

example()
```

------