xmp11.07 {Devore6} | 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. (2003) Probability and Statistics for Engineering and the Sciences (6th ed), Duxbury

(1976), ``Effects of plant density on tomato yields in western Nigeria'', Experimental Agriculture, 43-47.

### Examples

    data(xmp11.07)
    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))

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