glmtoolbox (version 0.1.12)

Trajan: Roots Produced by the Columnar Apple Cultivar Trajan.

Description

The data arose from a horticultural experiment to study the number of roots produced by 270 micropropagated shoots of the columnar apple cultivar Trajan. During the rooting period, all shoots were maintained under identical conditions. However, the shoots themselves were cultured on media containing different concentrations of the cytokinin 6-benzylaminopurine (BAP), in growth cabinets with an 8 or 16 hour photoperiod. The objective is to assess the effect of both the photoperiod and BAP concentration levels on the number of roots produced.

Usage

data(Trajan)

Format

A data frame with 270 rows and 4 variables:

roots

a numeric vector indicating the number of roots produced.

shoot

a numeric vector indicating the number of micropropogated shoots.

photoperiod

a factor indicating the photoperiod, in hours: 8 or 16.

bap

a numeric vector indicating the concentrations of the cytokinin 6-benzylaminopurine: 2.2, 4.4, 8.8 or 17.6.

References

Ridout M., Demétrio C.G., Hinde J. (1998). Models for count data with many zeros. In Proceedings of the XIXth international biometric conference, 179–192.

Ridout M., Hinde J., Demétrio C.G. (2001). A score test for testing a zero-inflated Poisson regression model against zero-inflated negative binomial alternatives. Biometrics 57:219-223.

Garay A.M., Hashimoto E.M., Ortega E.M.M., Lachos V. (2011). On estimation and influence diagnostics for zero-inflated negative binomial regression models. Computational Statistics & Data Analysis 55:1304-1318.

Examples

data(Trajan)
dev.new()
boxplot(roots ~ bap, data=subset(Trajan,photoperiod=="8"), at=c(1:4) - 0.15,
        col="blue", boxwex=0.2, xaxt="n", ylim=c(-0.5,17))
boxplot(roots ~ bap, data=subset(Trajan,photoperiod=="16"), add=TRUE,
        at=c(1:4) + 0.15, col="yellow", boxwex=0.2, xaxt="n")
axis(1, at=c(1:4), labels=levels(Trajan$bap))
legend("topright", legend=c("8","16"), title="Photoperiod", bty="n",
       fill=c("blue","yellow"))