| xmp11.07 {Devore5} | R Documentation |
The xmp11.07 data frame has 36 rows and 3 columns from an
experiment on the growth of different varieties of tomato plants at
different planting densities.
This data frame contains the following columns:
Devore, J. L. (2000) Probability and Statistics for Engineering and the Sciences (5th ed), Duxbury
(1976), ``Effects of plant density on tomato yields in western Nigeria'', Experimental Agriculture, 43-47.
data(xmp11.07)
xmp11.07$Variety <- factor(xmp11.07$Variety,
labels = c("Harvester", "Pusa Early Dwarf", "Ife No 1"))
## use an ordered factor for the density
xmp11.07$Density <- ordered(xmp11.07$Density,
labels = paste(1:4, "0000", sep = ""))
plot(Yield ~ Density, data = xmp11.07, col = "lightgray",
main = "Data from Example 11.7, page 450",
xlab = "Density (plants/hectare)")
means <- sapply(split(xmp11.07, xmp11.07$Density),
function(x) tapply(x$Yield, x$Variety, mean))
round(means, 2)
lines(1:4, means[1, ], col = 4, type = "b")
lines(1:4, means[2, ], col = 2, type = "b")
lines(1:4, means[3, ], col = 3, type = "b")
legend(0.4, 21.2, levels(xmp11.07$Variety), lty = 2,
col = c(4, 2, 3))
fm1 <- lm(Yield ~ Variety * Density, data = xmp11.07)
anova(fm1) # compare with Table 11.7, page 452
fm2 <- update(fm1, . ~ Variety + Density) # additive model
anova(fm2)
sort(tapply(xmp11.07$Yield, xmp11.07$Variety, mean))