sfsmisc (version 1.1-19)

potatoes: Fisher's Potato Crop Data

Description

Fisher's potato crop data set is of historical interest as an early example of a multi-factor block design.

Usage

data(potatoes)

Format

A data frame with 64 observations on the following 5 variables.

pos

a factor with levels 1:4.

treat

a factor with 16 levels A to H and J to Q, i.e., LETTERS[1:17][-9].

nitrogen

a factor specifying the amount of nitrogen sulfate (\(NH_4\)), with the four levels 0,1,2,4.

potash

a factor specifying the amount of potassium (K, ‘kalium’) sulfate, with the four levels 0,1,2,4.

yield

a numeric vector giving the yield of potatoes in ...

% << FIXME

References

T.Eden and R. A. Fisher (1929) Studies in Crop Variation. VI. Experiments on the Response of the Potato to Potash and Nitrogen. J. Agricultural Science 19, 201--213. Accessible from Bennett (1972), see above.

Examples

data(potatoes)
## See the experimental design:
with(potatoes, {
     cat("4 blocks of experiments;",
         "each does every (nitrogen,potash) combination (aka 'treat'ment) once.",
         '', sep="\n")
     print(ftable(table(nitrogen, potash, treat)))
     print(ftable(tt <- table(pos,potash,nitrogen)))
     tt[cbind(pos,potash,nitrogen)] <- as.character(treat)
     cat("The 4 blocks  pos = 1, 2, 3, 4:\n")
     ftable(tt)
     })
## First plot:
with(potatoes, interaction.plot(potash,nitrogen, response=yield))

## ANOVAs:
summary(aov(yield ~ nitrogen * potash + Error(pos), data = potatoes))
    # "==>" can use simply
summary(aov(yield ~ nitrogen + potash + pos, data = potatoes))
    # and
summary(aov(yield ~ nitrogen + potash, data = potatoes))