POLY_REGRESS: Polynomial Regression

Reference: Calculate a Polynomial Regression Column

POLY_REGRESS(options, degree, terms_generated,
        predictor_field1, predictor_field2, [...,] target_field)

where:

options

Reserved for future use.

degree

Integer

Is the degree of the polynomial. Low degree polynomials are recommended.

terms_generated

Keyword

Controls the terms that are generated in the polynomial equation.

ALL_TERMS generates the most general polynomial of degree degree based on the predictor fields.
INTERACTION_ONLY generates only terms linear in each predictor X0, X1, . . ., and cross-terms of the form X0*X1*X2 of at most degree predictors are used.

predictor_field1, predictor_field2, [...,]

Numeric

Are at least two predictor field names.

target_field

Numeric

Is the target field.

Example: Using POLY_REGRESS to Predict Income

The following scatter plot shows the predicted income values using polynomial regression of degree 4, with predictors education level, and age. The DEFINE FILE command creates virtual fields with correct numeric formats for use in the function.

DEFINE FILE wf_retail
EDUC_CODE/I2 TITLE 'Education Code'= DECODE
WF_RETAIL_EDUCATION_CUSTOMER.EDUCATION_DEGREE_TYPE (
'Professional Doctorates' 7,
'Doctorates' 6,
'Master''s Degrees' 5,
'Bachelor''s Degree' 4,
'Associate Degree' 3,
'High School' 2,
'No High School' 1,
ELSE 0);
END

GRAPH FILE wf_retail
PRINT
AGE
EDUC_CODE
COMPUTE PRED_INCOME/D20.2 =POLY_REGRESS('', 4, ALL_TERMS, 
                                        AGE, 
                                        EDUC_CODE,
                                        INCOME);
WHERE EDUC_CODE GT 0;
WHERE INCOME GT 12001.00;
WHERE AGE GT 21
ON TABLE PCHOLD
FORMAT JSCHART
ON TABLE SET LOOKGRAPH SCATTER
ON TABLE SET STYLE *
INCLUDE=IBFS:/FILE/IBI_HTML_DIR/ibi_themes/Warm.sty,$
TYPE=REPORT, CHART-ORIENTATION=HORIZONTAL, $
TYPE=DATA, COLUMN=N3, BUCKET=Y-AXIS, /*PRED_INCOME*/
$
TYPE=DATA, COLUMN=N1, BUCKET=X-AXIS, /*AGE*/
$
TYPE=DATA, COLUMN=N2, BUCKET=COLOR, /*EDUC_CODE*/
$
ENDSTYLE
END

The output is shown in the following image. Predicted income versus age is plotted, with education level as a parameter visualized by color.

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