{smcl} {* 15mar2002}{...} {hline} help for {hi:avplot2} {hline} {title:Partial regression plots for subsamples } {p 8 16}{cmd:avplot2} {it:varname} {cmd:,}{cmdab:sep:arate(}{it:varname}{cmd:)} [ {it:graph_options} ] {title:Description} {p}{cmd:avplot2} generates "partial regression plots" from an analysis of covariance model, where a category variable has been included in dummy-variable form among the regressors along with a constant term (that is, a dummy for all but one categories appears) and the full set of dummies have been interacted with a continuous variable. The "partial predictions" of such a model are then defined, for each category, as the category-specific constant term plus the category-specific slope multiplied by the continuous variable. Any number of additional covariates, continuous or discrete, may appear in the regression model, but do not affect the partial predictions. {title:Remarks} {p}One variable must be specified: the continuous variable which has been fully interacted in the regression model. If there are G categories of the discrete variable, the continuous variable must be included as G interaction terms, each named {it:categoryvarname} x {it:varname}. See the example below. {p}The separate option must specify the integer variable ({it:categoryvarname}) that defines the G categories. The model must contain (G-1) dummy variables for all but one category, and a constant term. It is immaterial which category is excluded. {title:Options} {p 0 4} {it:graph_options} are options of {cmd:graph, twoway}. One may use, for instance, the saving option to create a .gph file from the displayed graph. {p 4 4} The defaults include {cmd:connect(l)} for each subset of predicted values. {p 0 4} {cmd:separate(}{it:varname}{cmd:)} specifies the integer variable which defines categories. {title:Examples} {p 4 8}{inp:. use auto} {p 4 8}{inp:. drop if rep78==.} {p 4 8}{inp:. recode rep78 1/2=2} {p 4 8}{inp:. tab rep78,gen(repair)} {p 4 8}{inp:. rename rep78 repair} {p 4 8}{inp:. forv i=1/4 { g repair`i'xmpg = mpg*repair`i' } } {p 4 8}{inp:. reg price length foreign repair2-repair4 repair1xmpg repair2xmpg repair3xmpg repair4xmpg } {p 4 8}{inp:. avplot2 mpg, sep(repair) } {title:Author} Christopher F Baum, Boston College, USA baum@bc.edu {title:Acknowledgements} Nick Cox and his routines regplot and keyplot were indispensable in constructing this program. Development of the routine was inspired by conversations with Rebekah Coley and Jodi Morris. {title:Also see} {p 0 19}On-line: help for {help regress}, {help graph}, {help regdiag}, {help regplot} (if installed), {help sparl} (if installed) {p_end} {p 1 19}Manual: {hi: [U] 21 Programming Stata} {p_end}