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Publication date: 04/21/2023

Fit Special Window

In the Bivariate platform, use the Fit Special option to fit regression models with transformed variables. You can also constrain the slope and intercept, fit a polynomial model of specific degree, or center the polynomial.

The Fit Special option opens the Specify Transformation or Constraint window that contains the following options:

Y or X Transformation

Enables you to specify a transformation for the Y or X variable. The following transformations are available: natural logarithm, square root, square, reciprocal, and exponential.

Degree

Enables you to fit a polynomial of a specified degree.

Centered Polynomial

Enables you to center the polynomial. Deselect or select to disable or enable polynomial centering. Centering polynomials stabilizes the regression coefficients and reduces multicollinearity.

Note: Polynomial centering is not supported for transformations of the X variable.

Constrain Intercept to

Enables you to constrain the model intercept to a specified value.

Constrain Slope to

Enables you to constrain the model slope to a specified value.

Tip: To add the Y = X line to your plot select Fit Special and then select Constrain Intercept to: 0 and Constrain Slope to: 1.

For more information about the options in the Transformed Fit menu, see Bivariate Fit Options. For an example, see Example of the Fit Special Option.

Want more information? Have questions? Get answers in the JMP User Community (community.jmp.com).