Predicts the future behavior of a time series by using its historical behavior.

over_field_name property in your job, you cannot create a
forecast. For more information about this property, see Job resources.
duration
30d corresponds to 30 days. The default value is 1
  day. The forecast starts at the last record that was processed. For more
  information about time units, see Time units.
expires_in
0, the forecast is never automatically deleted.
  For more information about time units, see Time units.
You must have manage_ml, or manage cluster privileges to use this API.
For more information, see Security Privileges.
The following example requests a 10 day forecast for the total-requests job:
POST _ml/anomaly_detectors/total-requests/_forecast
{
  "duration": "10d"
}When the forecast is created, you receive the following results:
{
  "acknowledged": true,
  "forecast_id": "wkCWa2IB2lF8nSE_TzZo"
}You can subsequently see the forecast in the Single Metric Viewer in Kibana.