The data frame TIREWEAR contains measurements for the amount of tread loss in thousandths of an inch after 10,000 miles of driving.
TIREWEARA data frame with 16 observations on the following 3 variables:
wear (tread loss measured in thousandths of an inch)
treat (a factor with levels A, B, C, and D)
block (a factor with levels Car1, Car2, Car3, and Car4)
Ugarte, M. D., Militino, A. F., and Arnholt, A. T. 2015. Probability and Statistics with R, Second Edition. Chapman & Hall / CRC.
par(mfrow=c(1, 2), cex = 0.8)
with(data = TIREWEAR,
interaction.plot(treat, block, wear, type = "b", legend = FALSE))
with(data = TIREWEAR,
interaction.plot(block, treat, wear, type = "b", legend = FALSE))
par(mfrow=c(1, 1), cex = 1)