agridat (version 1.23)

gomez.nitrogen: Soil nitrogen at three times for eight fertilizer treatments

Description

Soil nitrogen at three times for eight fertilizer treatments

Format

A data frame with 96 observations on the following 4 variables.

trt

nitrogen treatment factor

nitro

soil nitrogen content, percent

rep

replicate

stage

growth stage, three periods

Details

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.

References

R-help mailing list, 9 May 2013. Data provided by Cyril Lundrigan. Analysis method by Rich Heiberger.

Examples

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))
          ))