I am running SAS 9.4 TS 1M6 on Windows.
In GLIMMIX, I had the following code:
effect splineaccent = spline(accent/naturalcubic details) ;
the results included:
25 |
50 |
75 |
which, to me, indicates 3 knots at 25, 50 and 75 but also
0 | |
1 | |
3 | 25 |
which I am not sure of. And the solutions for fixed effects showed 3 effects for spline. Are those 0-25, 25-50, 50-75 and an unshown (presumably 0) effect for 75 and up? Or is it the other way round (with the 0 effect for 0-25)? Or something else?
My article on "Regression with Cubic Splines" contains many references for splines and the EFFECT statement in SAS, including the doc and a SAS Usage Note.
Usage Note 57975: Understanding splines in the EFFECT statement
Doc on Splines and Spline Basis:
The three fixed effects are the spline basis functions, which you can output by using the OUTDESIGN= option on the PROC GLMSELECT statement, as shown in my article. Pictures of the spline basis functions are in the doc link. The fixed-effect model is in terms of the linear combinations of the spline basis functions.
My article on "Regression with Cubic Splines" contains many references for splines and the EFFECT statement in SAS, including the doc and a SAS Usage Note.
Usage Note 57975: Understanding splines in the EFFECT statement
Doc on Splines and Spline Basis:
The three fixed effects are the spline basis functions, which you can output by using the OUTDESIGN= option on the PROC GLMSELECT statement, as shown in my article. Pictures of the spline basis functions are in the doc link. The fixed-effect model is in terms of the linear combinations of the spline basis functions.
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