# Separate Analysis by Period

tmpar <- par( mar=c(3,3,0,0), mfcol=c(1,3) )

ylabs <- c("dry matter intake (DMI)","","")
xlabs <- c("(a) early period","(b) middle period","(c) late period")
names( xlabs ) <- names( ylabs ) <- levels( forage$per )

yaxis <- seq( 12, 24, 2 )
ylim <- log10( c(11.5,24.5) )

for ( i in levels( forage$per ) ) {
   tmpfor <- forage[forage$per==i, ]
   fit <- lm( log10( dmi )~trt*hc, tmpfor )
   tmpc <- ci.plot( fit, ylim=ylim, type="b", yaxt="n", xlab="", ylab="" )
   mtext( xlabs[i], 1, 2 )
   mtext( ylabs[i], 2, 2 )
   axis( 2, log10( yaxis ), yaxis )
   abline( h=forage.mean, lty=3 )
}

rm( ylabs, xlabs, tmpfor, fit, yaxis )

par( tmpar )