gomez.nonnormal3 {agridat} | R Documentation |
RCB of 12 rice varieties with leafhopper survival
data("gomez.nonnormal3")
A data frame with 36 observations on the following 3 variables.
gen
genotype/variety of rice
rep
replicate
hoppers
percentage of surviving leafhoppers
For each rice variety, 75 leafhoppers were caged and the percentage of surviving insects was determined.
Gomez suggest replacing 0 values by 1/(4*75) and replacing 100 by 1-1/(4*75) where 75 is the number of insects.
In effect, this means, for example, that (1/4)th of an insect survived.
Because the data are percents, Gomez suggested using the arcsin transformation.
Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 307.
Used with permission of Kwanchai Gomez.
None.
data(gomez.nonnormal3) dat <- gomez.nonnormal3 # First, replace 0, 100 values dat$thoppers <- dat$hoppers dat <- transform(dat, thoppers=ifelse(thoppers==0, 1/(4*75), thoppers)) dat <- transform(dat, thoppers=ifelse(thoppers==100, 100-1/(4*75), thoppers)) # Arcsin transformation of percentage p converted to degrees # is arcsin(sqrt(p))/(pi/2)*90 dat <- transform(dat, thoppers=asin(sqrt(thoppers/100))/(pi/2)*90) # QQ plots for raw/transformed data if(require(reshape2) & require(lattice)) qqmath( ~ value|variable, data=melt(dat), main="gomez.nonnormal3 - raw/transformed QQ plot", scales=list(relation="free")) m1 <- lm(thoppers ~ gen, data=dat) anova(m1) # Match Gomez table 7.25 ## Response: thoppers ## Df Sum Sq Mean Sq F value Pr(>F) ## gen 11 16838.7 1530.79 16.502 1.316e-08 *** ## Residuals 24 2226.4 92.77