Composing Functions (Advanced Usage)#
To see functions you can use with this syntax, checkout the aggregation functions and the transformation functions.
Any function with a parameter with the type signature [string or nested]
is able to accept the following as a value:
a string constant that represents a property of the model
an object of the form:
{ "alias_ref": "string", "nested_function": {"...": "..."} }
Only one of
alias_ref
ornested_function
may be present at a time. See the following explanations of each.
Alias References#
The alias_ref
field allows specifying another selected column’s alias
to use as input to the function. This example uses an alias_ref
to pull in another column
to the add
function:
{
"select": [
{
"function": "abs",
"alias": "absLoan",
"parameters": {
"property": "loan"
}
},
{
"function": "add",
"alias": "plus2",
"parameters": {
"left": 2,
"right": {
"alias_ref": "absLoan"
}
}
}
]
}
This request returns:
{
"query_result": [
{
"absLoan": 55.45,
"plus2": 57.45
}
]
}
Nested Functions#
The nested_function
field allows specifying another function definition
to use as input. Here’s an example of how to calculate absolute error for
a regression model. In this example, we pass the nested subtract
function as
input to the abs
function via the nested_function
object for the property
parameter of abs
:
{
"select": [
{
"function": "abs",
"alias": "abs_error",
"parameters": {
"property": {
"nested_function": {
"function": "subtract",
"alias": "error",
"parameters": {
"left": "Predicted_FICO_Score",
"right": {
"alias_ref": "ground_truth"
}
}
}
}
}
},
{
"property": "Predicted_FICO_Score"
},
{
"property": "Consumer_Credit_Score",
"alias": "ground_truth"
}
]
}
This query returns:
{
"query_result": [
{
"Consumer_Credit_Score": 660,
"Predicted_FICO_Score": 688.10004,
"abs_error": 28.100040000000035
},
{
"Consumer_Credit_Score": 663,
"Predicted_FICO_Score": 681,
"abs_error": 18
},
"..."
]
}
Note
If you use the same function multiple times in a query, you need to give each one a distinct “alias”. Otherwise, the names will conflict.