Forms factors to define terms representing the effects of one factor within another factor (R.W. Payne).
Options
LEVNULL = scalar |
Numerical value to represent the null level assigned to units not involved in the comparison of the levels of one of the factors within a particular level of the other factor; default 0 |
LABNULL = text |
String to label the null level; default '-' |
Parameters
F1 = factors |
First factor |
F2 = factors |
Second factor |
F1WITHINF2 = pointers |
Pointer containing a factor for each level of the second factor, used to estimate the effects of the first factor within that level |
F2WITHINF1 = pointers |
Pointer containing a factor for each level of the first factor, used to estimate the effects of the second factor within that level |
Description
When there is an interaction between two factors, it may be interesting to compare the effects of one factor within each level of the other factor. FWITHINTERMS forms factors to define terms to enable you to do this.
The two factors are specified by the F1 and F2 parameters. The F1WITHINF2 parameter saves a pointer containing a factor for each level of the F2 factor, to be used to assess the effects of F1 within that level. To do this you can specify a model formula of
F2 / F1WITHINF2[]
The term F2 represents the main effect of factor F2. Subsequent terms like F2.F1WITHINF2[i] represent the effects of F1 within level i of factor F2. To help make the output clear, the elements of F1WITHINF2 are labelled by the levels of F2 (or its labels if available). Each factor has the levels of F1 for the units with its corresponding level of F2, and a “null” level elsewhere. The numerical value to represent the null level is specified by the LEVNULL option (default 0). If F1 has labels, the label for the null level is specified by the LABNULL option (default '-').
Similarly, the F2WITHINF1 parameter saves a pointer containing factors to assess the effects of F2 within F1.
Options: LEVNULL, LABNULL.
Parameters: F1, F2, F1WITHINF2, F2WITHINF1.
See also
Procedure: FBETWEENGROUPVECTORS.
Commands for: Calculations and manipulation, Analysis of variance.
Example
CAPTION 'FWITHINTERMS example',\
!t('Experiment on canola with two treatment factors,',\
'N (nitrogen) and S (sulphur), in a randomized-block design');\
STYLE=meta,plain
SPLOAD [PRINT=*] '%data%/Canola.gsh'
BLOCK block / plot
TREATMENTS N * S
ANOVA [PRINT=aovtable,means; FPROBABILITY=yes] yield
FWITHINTERMS F1=S; F2=N; F1WITHINF2=SwithinN; F2WITHINF1=NwithinS
PRINT N,S,SwithinN[],NwithinS[]; DECIMALS=0
" sulphur within nitrogen "
TREATMENTS N / SwithinN[]
ANOVA [PRINT=aovtable,means; FPROBABILITY=yes] yield
" nitrogen within sulphur "
TREATMENTS S / NwithinS[]
ANOVA [PRINT=aovtable,means; FPROBABILITY=yes] yield