How to: |

MULTIREGRESS derives a linear equation that best fits a set of numeric data points, and uses this equation to create a new column in the report output. The equation can be based on one or more independent variables.

The equation generated is of the following form, where y is the dependent variable and x1, x2, and x3 are the independent variables.

y = a1*x1 [+ a2*x2 [+ a3*x3] ...] + b

When there is one independent variable, the equation represents a straight line. When there are two independent variables, the equation represents a plane, and with three independent variables, it represents a hyperplane. You should use this technique when you have reason to believe that the dependent variable can be approximated by a linear combination of the independent variables.

MULTIREGRESS(input_field1, [input_field2, ...])

where:

`input_field1`,`input_field2`...-
Are any number of field names to be used as the independent variables. They should be independent of each other. If an input field is non-numeric, it will be categorized to transform it to numeric values that can be used in the linear regression calculation.

The following request uses the DOLLARS and BUDDOLLARS fields to generate a regression column named Estimated_Dollars.

GRAPH FILE GGSALES SUM BUDUNITS UNITS BUDDOLLARS DOLLARS COMPUTE Estimated_Dollars/F8 = MULTIREGRESS(DOLLARS, BUDDOLLARS); BY DATE ON GRAPH SET LOOKGRAPH LINE ON GRAPH PCHOLD FORMAT JSCHART ON GRAPH SET STYLE * INCLUDE=IBFS:/FILE/IBI_HTML_DIR/ibi_themes/Warm.sty,$ type=data, column = n1, bucket = x-axis,$ type=data, column= dollars, bucket=y-axis,$ type=data, column= buddollars, bucket=y-axis,$ type=data, column= Estimated_Dollars, bucket=y-axis,$ *GRAPH_JS "series":[ {"series":2, "color":"orange"}] *END ENDSTYLE END

The output is shown in the following image. The orange line represents the regression equation.

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