index.AMMI {agricolae} | R Documentation

## AMMI index and yield stability

### Description

calculate AMMI stability value (ASV) and Yield stability index (YSI).

### Usage

    index.AMMI(model)

### Arguments

`model` | object AMMI

### Details

AMMI stability value (ASV) was calculated using the following formula, as suggested by Purchase (1997)

ASV = sqrt(SSpc1/SSpc2 *(PC1i)^2+(PC2i)^2)

YSI = RASV + RY

RASV = rank(ASV) and RY = rank(Y across by environment)

### Value

`ASV` | AMMI stability value
`YSI` | Yield stability index
`rASV` | Rank of AMMI stability value
`rYSI` | Rank of yield stability index
`means` | average genotype by environment

### Author(s)

F. de Mendiburu

### References

The use of an AMMI model and its parameters to analyse yield stability in multienvironment trials. N. SABAGHNIA, S.H. SABAGHPOUR AND H. DEHGHANI. Journal of Agricultural Science (2008), 146, 571-581. f 2008 Cambridge University Press 571 doi:10.1017/S0021859608007831 Printed in the United Kingdom

Parametric analysis to describe genotyperenvironment interaction and yield stability in winter wheat. PURCHASE, J. L. (1997). Ph.D. Thesis, Department of Agronomy, Faculty of Agriculture of the University of the Free State, Bloemfontein, South Africa.

### See Also

`AMMI`,`plot.AMMI`

### Examples

    library(agricolae)
    # Index AMMI
    data(plrv)
    model<- with(plrv,AMMI(Locality, Genotype, Rep, Yield, console=FALSE))
    Idx<-index.AMMI(model)
    names(Idx)
    # Crops with improved stability according AMMI.
    print(Idx[order(Idx[,3]),])
    # Crops with better response and improved stability according AMMI.
    print(Idx[order(Idx[,4]),])

[Package agricolae version 1.2-9 Index]