khannaekta commented on code in PR #615:
URL: https://github.com/apache/madlib/pull/615#discussion_r1511750633
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src/ports/postgres/modules/pmml/table_to_pmml.sql_in:
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@@ -146,10 +144,25 @@ Alternatively, the above can also be invoked as below if
custom names are needed
for fields in the Data Dictionary:
<pre class="example">
SELECT madlib.pmml('patients_logregr',
- 'out_attack~1+in_trait_anxiety+in_treatment');
+ 'out_attack~in_trait_anxiety+in_treatment');
</pre>
-\b Note: If the second argument of 'pmml' function is not specified, a default
suffix "_pmml_prediction" will be automatically append to the column name to be
predicted. This can help avoid name conflicts.
+\b Note: 1. If the second argument of 'pmml' function is not specified, a
default suffix "_pmml_prediction" will be automatically append to the column
name to be predicted. This can help avoid name conflicts.
+
+\b Note: 2. While training regression models, it is possible to use a non
array expression. Consider this example:
+<pre>
+-- Create a table where a column named 'x' is an array of the independent
variables
+CREATE TABLE patients2 AS SELECT second_attack AS y, ARRAY[1, treatment,
trait_anxiety] AS x from patients;
+
+-- Now use the columns 'x' and 'y' created in the previous step
+SELECT madlib.logregr_train(
+ 'patients2',
+ 'patients_logregr2',
+ 'y',
+ 'x');
+</pre>
+In such scenarios, the pmml code always assumes that the intercept variable
"1," was already included in the independent variable
+expression. If it is not included, the exported PMML would be incorrect.
Review Comment:
will reword this to : `If it is not included, the exported PMML would not
explicitly capture it as intercept.`
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