safety_first_index {toolStability}

Safety-first Index

Description

safety_first_index calculate variance of a genotype across environments.

Usage

safety_first_index(data, trait, genotype, environment, lambda)

Arguments

data

a dataframe containing trait, genotype and environment.

trait

colname of a column containing a numeric vector of interested trait to be analyzed.

genotype

colname of a column containing a character or factor vector labeling different genotypic varieties.

environment

colname of a column containing a character or factor vector labeling different environments.

lambda

the minimal acceptable value of trait that the user expected from crop across environments. Lambda should between the ranges of trait vlaue.

Details

Safety-first index (Eskridge, 1990) is calculated based on the assumption of that the trait from each genotype follows normal distribution over enviornments. Among different environments, trait below a given cirtical level \lambda is defined as failure of trait. The probability of trait failure can be obtained by entering mean and variance of trait and \lambda into the cumulated density function of normal distribution. Variety with low safety first index is considered as stable. Equation of adjusted coefficient of variation can be found in vignette file.

Value

a data table with coefficient of determination

Author(s)

Tien-Cheng Wang

References

Eskridge KM (1990). “Selection of Stable Cultivars Using a Safety-First Rule.” Crop Science, 30(2), 369. ISSN 0011-183X, doi: 10.2135/cropsci1990.0011183X003000020025x.

Examples

data(Data)
safety.first.index <- safety_first_index(
 data = Data,
 trait = "Yield",
 genotype = "Genotype",
 environment = "Environment",
 lambda = median(Data$Yield))