Basic Analysis and Graphing - SAS

Chapter 4 Performing Bivariate Analysis 97
Fitting Commands and General Options
Table 4.2 Descriptions of the Fitting Commands (Continued)
Fit Orthogonal
Density Ellipse
Nonpar Density
Fits lines that adjust for variability in X as well as
Y.
Draws an ellipse that contains a specified mass of
points.
Shows patterns in the point density, which is
useful when the scatterplot is so darkened by
points that it is difficult to distinguish patterns.
See “Fit Orthogonal” on
page 110.
See “Density Ellipse” on
page 111.
See “Nonpar Density” on
page 113.
Note: You can remove a fit using the Remove Fit command. For details, see “Fitting Menu Options” on
page 115.
Fitting Command Categories
Fitting command categories include regression fits and density estimation.
Category Description Fitting Commands
Regression Fits
Density Estimation
Regression methods fit a curve through the points. The
curve is an equation (a model) that is estimated using least
squares, which minimizes the sum of squared differences
from each point to the line (or curve). Regression fits
assume that the Y variable is distributed as a random
scatter above and below a line of fit.
Density estimation fits a bivariate distribution to the
points. You can either select a bivariate normal density,
characterized by elliptical contours, or a general
nonparametric density.
Fit Mean
Fit Line
Fit Polynomial
Fit Special
Fit Spline
Fit Each Value
Fit Orthogonal
Fit Density Ellipse
Nonpar Density
Fit the Same Command Multiple Times
You can select the same fitting command multiple times, and each new fit is overlaid on the scatterplot. You
can try fits, exclude points and refit, and you can compare them on the same scatterplot.
To apply a fitting command to multiple analyses in your report window, hold down the CTRL key and
select a fitting option.