[R] Fit lines in intxplot

[arun]

Dear R help,

I tried to add linear fit lines in intxplot by adding "index.cond = function(x,y) coef(lm(y ~ x))[1]" inside the intxplot().  It didn't help.  I would appreciate any help.
My dataset and codes are pasted below.

Thanks,
A.K.


datGreen<- read.table(text="
Time,    DarkSt,    LightSt
0,    0,    1
1,    0.03,    0.82
2,    0.06,    0.91
3,    0.12,    0.64
4,    0.12,    0.73
5,    0.12,    0.64
6,    0.09,    0.64
7,    0.09,    0.64
8,    0.09,    0.64
9,    0.09,    0.64
10,    0.12,    0.64
11,    0.09,    0.64
12,    0.09,    0.73
13,    0.06,    0.73
14,    0.06,    0.64
15,    0.09,    0.73
16,    0.09,    0.73
17,    0.09,    0.73
18,    0.12,    0.64
19,    0.09,    0.64
20,    0.12,    0.64
",sep=",",header=TRUE)

dat1<-data.frame(time=rep(c(1:20),rep(2,20)),trt=rep(c('D','L'),each=1))
    datG<-data.frame(matrix(rbind(datGreen$DarkSt,datGreen$LightSt),ncol=1,byrow=TRUE))
    colnames(datG)<-"Response"
    dat2G<-datG[-1,]
    dat2G<-data.frame(dat2G)
    dat2G<-dat2G[-1,]
    dat2G<-data.frame(dat2G)
    colnames(dat2G)<- "Response"
    dat3G<-data.frame(dat1,dat2G)
    dat4G<-transform(dat3G,trt=ordered(trt,levels=c('D','L')))    
     dat4G$time<-factor(dat4G$time)
    position(dat4G$time)<-as.numeric(levels(dat4G$time))
    position(dat4G$trt)<-c(10,20)
#pdf("GreenDarkvsLight.pdf")
intxplot(Response~time,data=dat4G,groups=trt,se=TRUE,ylim=c(0,1),main="Response in Green light")

#dev.off()

I expect to get fit lined as in the xyplot:
xyplot(Response ~ time, dat4G, 
              type = c( "g", "p","r"), groups=trt, index.cond = function(x,y) coef(lm(y ~ x))[1],
             xlab = "Time in min",
             ylab = "Response", main="Response in Green light")