Soil nitrogen at three times for eight fertilizer treatments
Soil nitrogen at three times for eight fertilizer treatments
A data frame with 96 observations on the following 4 variables.
trtnitrogen treatment factor
nitrosoil nitrogen content, percent
repreplicate
stagegrowth stage, three periods
Eight fertilizer treatments were tested.
Soil nitrogen content was measured at three times. P1 = 15 days post transplanting. P2 = 40 days post transplanting. P3 = panicle initiation.
Used with permission of Kwanchai Gomez.
Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 259.
R-help mailing list, 9 May 2013. Data provided by Cyril Lundrigan. Analysis method by Rich Heiberger.
## Not run:
library(agridat)
data(gomez.nitrogen)
dat <- gomez.nitrogen
# Note the depletion of nitrogen over time (stage)
libs(HH)
interaction2wt(nitro ~ rep/trt + trt*stage, data=dat,
x.between=0, y.between=0,
main="gomez.nitrogen")
# Just the fertilizer profiles
with(dat, interaction.plot(stage, trt, nitro,
col=1:4, lty=1:3, main="gomez.nitrogen",
xlab="Soil nitrogen at three times for each treatment"))
# Gomez table 6.16
m1 <- aov(nitro ~ Error(rep/trt) + trt*stage, data=dat)
summary(m1)
# Gomez table 6.18
# Treatment 1 2 3 4 5 6 7 8
cont <- cbind("T7 vs others" = c( 1, 1, 1, 1, 1, 1,-7, 1),
"T8 vs others" = c( 1, 1, 1, 1, 1, 1, 0,-6),
"T2,T5 vs others" = c(-1, 2,-1,-1, 2,-1, 0, 0),
"T2 vs T5" = c( 0, 1, 0, 0,-1, 0, 0, 0))
contrasts(dat$trt) <- cont
contrasts(dat$trt)
m2 <- aov(nitro ~ Error(rep/trt) + trt*stage, data=dat)
summary(m2, expand.split=FALSE,
split=list(trt=list(
"T7 vs others"=1,
"T8 vs others"=2,
"T2,T5 vs others"=3,
"T2 vs T5"=4,
rest=c(5,6,7)),
"trt:stage"=list(
"(T7 vs others):P"=c(1,8),
"(T8 vs others):P"=c(2,9),
"(T2,T5 vs others):P"=c(3,10),
"(T2 vs T5):P"=c(4,11),
"rest:P"=c(5,6,7,12,13,14))
))
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