xmp11.07 {Devore5}R Documentation

data from Example 11.7

Description

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.

Format

This data frame contains the following columns:

Yield
a numeric vector giving the yields for each plot
Variety
a numeric vector coding the variety.
Density
a numeric vector giving the planting density (thousands of plants per hectare).

Details

Source

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.

Examples

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))