%sp_plotbx1x2
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   Creates an animated  3 dimensional plot of a regression surface 
   with a changing interaction coefficient

Description

  The %sp_plotbx1x2 macro will create an animated 3 dimensional plot  
  of a regression surface based on the coefficients from two   
  predictors and their interaction in a regression equation. The graph 
  changes as the interaction incrementally changes between a specified 
  minimum and maximum value.  The graph can be saved as a .gif file  
  and used in a web page.  The individual plots that make up the 
  animated gif can be viewed individually in the graph window of SAS.
  The code for this macro should end in a semicolon in order to avoid 
  unnecessary error messages in the log file.


Syntax

  %sp_plotbx1x2(outfile="c:\sp_plotbx1x2.gif", data=_spinplt,
            x1lo=-10, x1hi=10, x1by=1, x2lo=-10, x2hi=10, x2by=1,
            cons=0, bx1=0, bx2=0, bx1x2=0, bx1x1=0, bx2x2=0, 
            bx1x1x2=0, bx1x2x2=0, 
            dev=gif373, title=Spin Plot, 
            cmd=plot, plot=, gopt=, angle=100, slen=6, 
            bx1x2_lo=-5, bx1x2_hi=5, bx1x2_by=1 ); 


    _spinplt - name of dataset where data created to be plotted in 
               graph is saved
    x1lo     - the minimum value of the range of x1
    x1hi     - the maximum value of the range of x1
    x1by     - the spacing of the grid of the regression surface
    x2lo     - the minimum value of the range of x2
    x2hi     - the maximum value of the range of x2
    x2by     - the spacing of the grid of the regression surface  
    const    - the value of the constant in the regression function
    bx1      - the value of the coefficient of x1 in the regression 
               function
    bx2      - the value of the coefficient of x2 in the regression 
               function
    bx1x2    - the value of the coefficient of x1*x2 in the  
               regression function
    bx1x1    - the value of the coefficient of x1*x1 in the  
               regression function
    bx2x2    - the value of the coefficient of x2*x2 in the  
               regression function
    bx1x1x2  - the value of the coefficient of x1*x1*x2 in the 
               regression function
    bx1x2x2  - the value of the coefficient of x1*x2*x2 in the 
               regression function
    outfile  - saves the graph as a .gif file with the given name    
    data     - saves the data with the given name
    dev      - specifies the graphic device used 
    title    - the title displayed at the top of the graph
    cmd      - specifies if the graph is a plot (the data points 
               define a surface) or a scatter plot (represents 
               each data point with a specified shape, the default  
               is a pyramid)
    plot     - specifies other options for the graph, the options 
               available will depend on whether cmd was specified 
               as scatter or plot (plot is the default) 
    gopt     - specifies other goptions which can modify the 
               detailed options on the size, color or the style of 
               the plot
    angle    - the angle the plot is viewed at
    slen     - the length of the coefficient of x1 in the title 
    bx1x2_lo - the minimum value of the coefficient of x1
    bx1x2_hi - the maximum value of the coefficient of x1
    bx1x2_by - the incriments that the bx1 is changing by, must be a 
               positive number
     


Examples

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2a.gif');

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2b.gif', cons=3, bx1=1, bx2=-2);

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2c.gif',bx1x2=-1,
                bx1_lo=2, bx1_hi=8, bx1_by=1, slen=4);

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2d.gif',
                cons=1, bx2=1.7, bx1x2=-.5, plot=grid,
                title=Great Plot!);

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2e.gif',
	        cons=0, bx2=.5, bx1x2=-.4,
                plot=grid cbottom=cyan ctop=purple, 
                bx1_lo=-2, bx1_hi=4, bx1_by=1);

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2f.gif',
                bx2=1.7, bx1x2=.5,  
                plot= grid ctop=cyan cbottom=blue caxis=green); 

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2g.gif', cons=0, bx2=3,
                slen=6, cmd=scatter, gopt= delay=10,
                plot= shape='balloon' noneedle size=.6);          

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2h.gif',
                bx1x2=-1.5 , cmd=scatter, 
                plot= noneedle shape='spade' size=.8, gopt = border); 

  %sp_plotbx1x2(outfile='c:\sp_plotbx1x2i.gif', bx1x2x2=.1);



Author

  Michael Mitchell
  mnm@ucla.edu
  UCLA Academic Technology Services
  Statistical Consulting Group
  
Also See

  See a complete example in
    http://www.ats.ucla.edu/stat/sas/examples/aw/example_graphs.htm 
    http://www.ats.ucla.edu/stat/sas/teach/reg_int/reg_int_cont.htm
  
  For more details about the cmd, plot and gopt options please refer
    to following sections in the SAS Manuals
    http://sasdocs.ats.ucla.edu/gref/z3d-plot.htm
    http://sasdocs.ats.ucla.edu/gref/zscatter.htm
    http://sasdocs.ats.ucla.edu/gref/zonschap.htm
    
  Also see the macro itself from 
   http://www.ats.ucla.edu/stat/sas/macros/sp_plotbx1x2.sas.txt
           
  Also see the books (http://www.ats.ucla.edu/stat/books/ )
    Multiple Regression: Testing and Interpreting Interactions 
      by Leona S. Aiken and Steven G. West 
    Interaction Effects in Multiple Regression by James Jaccard, 
      Robert Turrisi and Choi K. Wan