# Transformation Functions

For transformation functions, it will be helpful to include `property` in the request to help associate the transformation function values, for example:

```json
{
    "select": [
        {
            "property": "<attribute_name> [string]"
        },
        {
            "function": "roundTimestamp",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "property": "<attribute_name> [string]",
                "time_interval": "[second|minute|hour|day|month|year]"
            }
        }
    ]
}
```

We omit `property` for brevity in the following examples.

For an explanation of nested functions, see the guide {doc}`composing_functions`.

### Round Timestamp
Rounds a timestamp property to the provided time interval. This function requires one property 
which must be an attribute of type datetime and one parameter, `time_interval`.

Query Request:
```json
{
    "select": [
        {
            "function": "roundTimestamp",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "property": "<attribute_name> [string or nested]",
                "time_interval": "[second|minute|hour|day|month|year]"
            }
        }
    ]
}
```

Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "<rounded_timestamp> [string]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "roundTimestamp",
            "parameters": {
                "property": "inference_timestamp",
                "time_interval": "day"
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "roundTimestamp": "2020-08-10T00:00:00.000Z"
        },
        {
            "roundTimestamp": "2020-08-09T00:00:00.000Z"
        },
        {
            "roundTimestamp": "2020-08-08T00:00:00.000Z"
        }
    ]
}
```
[back to top](#transformation-functions)

### Label By Max Column
Given a list of columns, returns a string column with the name of the column containing the max value for the row. For example, this function can be used to extract the max probability from a vector of probability properties.

Query Request:
```json
{
    "select": [
        {
            "function": "labelByMaxColumn",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "properties": [
                    "<property name> [string]"
                ]
            }
        }
    ]
}
```

Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "<one of the properties from the given list> [string]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "labelByMaxColumn",
            "alias": "classPrediction",
            "parameters": {
                "properties": [
                    "class_1",
                    "class_2",
                    "class_3"
                ]
            }
        }
    ]
}
```
Sample Response:
```json
{
    "classPrediction": [
        {
            "classPrediction": "class_1"
        },
        {
            "classPrediction": "class_1"
        },
        {
            "classPrediction": "class_2"
        }
    ]
}
```
[back to top](#transformation-functions)

### Bin Continuous 
This function bins a continuous value based on supplied thresholds. The bins will be formed as: 
`[< threshold_1, threshold_1 <= x < threshold_2, ... , threshold_(n-1) <= x < threshold_(n), threshold_(n) < x]`.
The response bins will be labeled with an integer id corresponding to the ordered bin, starting at 1. 
If `n` thresholds are given, `n+1` bins will be returned.

Query Request:
```json
{
    "select": [
        {
            "function": "binContinuous",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "property": "<property name> [string or nested]",
                "bin_thresholds": [
                    "<threshold_1> [number]",
                    "<threshold_2> [number]",
                    "<threshold_3> [number]"
                ]
            }
        }
    ]
}
```

Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "<bin_id> [int]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "property": "age"
        },
        {
            "function": "binContinuous",
            "alias": "ageBin",
            "parameters": {
                "property": "age",
                "bin_thresholds": [
                    18,
                    65,
                    95
                ]
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "age": 10,
            "ageBin": 1
        },
        {
            "age": 20,
            "ageBin": 2
        },
        {
            "age": 70,
            "ageBin": 3
        }
    ]
}
```
[back to top](#transformation-functions)
### Bins To Quantiles
Returns an array of values representing the quantiles based on the number of bins passed to the function. 
For example if you supply `"num_bins": "10"`, then this query will return the value in your data at the 
10%, 20%, ... , 90%, 100% quantiles.  

Query Request:
```json
{
    "select": [
        {
            "function": "binsToQuantiles",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "property": "<attribute_name> [string or nested]",
                "num_bins": "<num_bins> [int]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": [
                "float"
            ]
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "binsToQuantiles",
            "alias": "quantiles",
            "parameters": {
                "property": "age",
                "num_bins": 10
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": [
                19,
                28,
                37,
                46,
                55,
                64,
                73,
                82,
                91
            ]
        }
    ]
}
```
[back to top](#transformation-functions)

### Date Diff
Returns the difference of two timestamps in `unit`s. Valid units are: 
`second`, `minute`, `hour`, `day`, `week`, `month`, `quarter`, and `year`.

Query Request:
```json
{
    "select": [
        {
            "function": "dateDiff",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "unit": "[second|minute|hour|day|week|month|quarter|year]",
                "start_date": "<attribute_name> [string or nested]",
                "end_date": "<attribute_name> [string or nested]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "difference [int]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "dateDiff",
            "alias": "date_diff",
            "parameters": {
                "unit": "second",
                "start_date": "inference_timestamp",
                "end_date": "prev_timestamp"
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "date_diff": 100
        }
    ]
}
```
[back to top](#transformation-functions)


### Neighbor
Returns the value of the column `offset` rows next to this row in the ordering.
`default` is the value that is returned when the offset goes out of bounds on the row set. 
It is recommended to use this function in a subquery with an `order_by` clause to get consistent ordering.

Query Request:
```json
{
    "select": [
        {
            "function": "neighbor",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "offset": "<offset> [int]",
                "property": "<attribute_name> [string or nested]",
                "default": "<default_value> [any]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "neighbor_value [any]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "neighbor",
            "alias": "prev_timestamp",
            "parameters": {
                "property": "inference_timestamp",
                "offset": -1,
                "default": null
            }
        }
    ],
    "order_by": [
        {
            "property": "inference_timestamp",
            "direction": "desc"
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "prev_timestamp": "2021-06-15T00:00:00.000Z"
        }
    ]
}
```
[back to top](#transformation-functions)


### Arithmetic
`add`, `subtract`, `multiply`, and `divide` are valid arithmetic functions. 
Each takes two columns as input and returns the result of the arithmetic expression.

Query Request:
```json
{
    "select": [
        {
            "function": "[add|subtract|multiply|divide]",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "left": "<attribute_name> [string or nested]",
                "right": "<attribute_name> [string or nested]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "expression_result [number]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "multiply",
            "alias": "double_home_value",
            "parameters": {
                "left": "Home_Value",
                "right": 2
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "double_home_value": 20000
        }
    ]
}
```

Sample nested request to compute `(Home_Value + Car_Value) * 2`
```json
{
    "select": [
        {
            "function": "multiply",
            "alias": "double_loans",
            "parameters": {
                "left": {
                    "nested_function": {
                        "function": "add",
                        "alias": "total_loan",
                        "parameters": {
                            "left": "Home_Value",
                            "right": "Car_Value"
                        }
                    }
                },
                "right": 2
            }
        }
    ]
}
```
Sample Nested Response:
```json
{
    "query_result": [
        {
            "double_loans": 20000
        }
    ]
}
```
[back to top](#transformation-functions)


### Absolute Value
Take the absolute value of a property.

Query Request:
```json
{
    "select": [
        {
            "function": "abs",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "property": "<attribute_name> [string or nested]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "<abs_value> [float]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "abs",
            "alias": "abs_delta",
            "parameters": {
                "property": "delta"
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "abs_delta": 55.45
        }
    ]
}
```
[back to top](#transformation-functions)

### Logical Functions
`equals`, `and`, and `or` are valid logical functions. Each takes two columns as input and returns the result of the logical expression. These follow the same API as [Arithmetic Functions](#arithmetic)

Query Request:
```json
{
    "select": [
        {
            "function": "[equals|and|or]",
            "alias": "<alias_name> [optional string]",
            "parameters": {
                "left": "<attribute_name> [string or nested]",
                "right": "<attribute_name> [string or nested]"
            }
        }
    ]
}
```
Query Response:
```json
{
    "query_result": [
        {
            "<function_name/alias_name>": "expression_result [0 or 1]"
        }
    ]
}
```

Sample Request:
```json
{
    "select": [
        {
            "function": "equals",
            "alias": "has_phd",
            "parameters": {
                "left": "education",
                "right": 4
            }
        }
    ]
}
```
Sample Response:
```json
{
    "query_result": [
        {
            "has_phd": 1
        }
    ]
}
```

Sample nested request to compute `has_phd` or `has_masters`
```json
{
    "select": [
        {
            "function": "or",
            "alias": "has_higher_education",
            "parameters": {
                "left": {
                    "nested_function": {
                        "function": "equals",
                        "alias": "has_phd",
                        "parameters": {
                            "left": "education",
                            "right": 4
                        }
                    }
                },
                "right": {
                    "nested_function": {
                        "function": "equals",
                        "alias": "has_masters",
                        "parameters": {
                            "left": "education",
                            "right": 3
                        }
                    }
                }
            }
        }
    ]
}
```
Sample Nested Response:
```json
{
    "query_result": [
        {
            "has_higher_education": 1
        }
    ]
}
```
[back to top](#transformation-functions)