[R] Adding a regression line to an xyplot

[David Winsemius]

On Feb 14, 2010, at 6:33 PM, Andrew McFadden wrote:

> Hi R users
>
>> I am trying to add a regression line to a graph for "c" for factor 2
>> only. Any suggestions?
>>
> library(lattice)
>
> a=(1:10)
> b=c(1:5,16:20)
> c=as.factor(c(rep(1,5),rep(2,5)))
>
> d=data.frame(a,b,c)
>
> xyplot(a~b, pch=c(6,8),data = tavg, groups=d$c,

Seems likely that you want the dataframe defined above to be used as  
the argument to
'data='. Otherwise xyplot throws an error unless "tavg" is defined  
elsewhere.

If so, then try:

tavg=data.frame(a,b,c)

xyplot(a~b, pch=c(6,8),data = tavg, groups=c,
  panel=function(x,y, groups,...) {
            panel.xyplot(x,y,groups,type=c("p"),...);
            panel.lmline(x[c=="2"],y[c=="2"],groups,...)},
   xlab="a",ylab="b")

> reg.line=lm, smooth=FALSE, type=c("p","g"),xlab="a",ylab="b")
>
>> I would appreciate your help.
>>
>> Kind regards
>>
>> andy
>>
>> Andrew McFadden MVS BVSc
>> Incursion Investigator
>> Investigation & Diagnostic Centres - Wallaceville Biosecurity New
>> Zealand Ministry of Agriculture and Forestry
>>
>> Phone 04 894 5600 Fax 04 894 4973 Mobile 029 894 5611 Postal address:
>> Investigation and Diagnostic Centre- Wallaceville Box 40742 Ward St
>> Upper Hutt
>>
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT