PredictHistogram (DMX)

Άρθρο
03/03/2023

Applies to: SQL Server Analysis Services

Returns a table that represents a histogram for the prediction of a given column.

Syntax

  
PredictHistogram(<scalar column reference> | <cluster column reference>)

Applies To

A scalar column reference or a cluster column reference. Can be used with all algorithm types except the Microsoft Association algorithm.

Return Type

A table.

Remarks

A histogram generates statistics columns. The column structure of the returned histogram depends on the type of column reference that is used with the PredictHistogram function.

Scalar Columns

For a <scalar column reference>, the histogram that the PredictHistogram function returns consists of the following columns:

The value that is being predicted.
$Support
$Probability
$ProbabilityVariance

Microsoft data mining algorithms do not support $ProbabilityVariance. This column always contains 0 for Microsoft algorithms.
$ProbabilityStdev

Microsoft data mining algorithms do not support $ProbabilityStdev. This column always contains 0 for Microsoft algorithms.
$AdjustedProbability

The $AdjustedProbability column is an Analysis Services extension to the Microsoft OLE DB for Data Mining specification.

Cluster Columns

The histogram that the PredictHistogram function returns for a <cluster column reference> consists of the following columns:

$Cluster (represents the cluster name)
$Distance
$Probability

Examples

The following example returns the predicted state of the Bike Buyer column in a singleton query. The query also returns the top two most likely states of the Bike Buyer attribute, based on the adjusted probability obtained by using the PredictHistogram function.

SELECT  
  [TM Decision Tree].[Bike Buyer],  
  TopCount(PredictHistogram([Bike Buyer]),$AdjustedProbability,3)  
From  
  [TM Decision Tree]  
NATURAL PREDICTION JOIN  
(SELECT 28 AS [Age],  
  '2-5 Miles' AS [Commute Distance],  
  'Graduate Degree' AS [Education],  
  0 AS [Number Cars Owned],  
  0 AS [Number Children At Home]) AS t

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