ASTAB.AMMI {ammistability} R Documentation

## AMMI Based Stability Parameter

### Description

ASTAB.AMMI computes the AMMI Based Stability Parameter (ASTAB) (Rao and Prabhakaran 2005) considering all significant interaction principal components (IPCs) in the AMMI model. Using ASTAB, the Simultaneous Selection Index for Yield and Stability (SSI) is also calculated according to the argument ssi.method.

### Usage

ASTAB.AMMI(model, n, alpha = 0.05, ssi.method = c("farshadfar", "rao"), a = 1)


### Arguments

 model The AMMI model (An object of class AMMI generated by AMMI). n The number of principal components to be considered for computation. The default value is the number of significant IPCs. alpha Type I error probability (Significance level) to be considered to identify the number of significant IPCs. ssi.method The method for the computation of simultaneous selection index. Either "farshadfar" or "rao" (See SSI). a The ratio of the weights given to the stability components for computation of SSI when method = "rao" (See SSI).

### Details

The AMMI Based Stability Parameter value ($$ASTAB$$) (Rao and Prabhakaran 2005) is computed as follows:

$ASTAB = \sum_{n=1}^{N'}\lambda_{n}\gamma_{in}^{2}$

Where, $$N'$$ is the number of significant IPCs (number of IPC that were retained in the AMMI model via F tests); $$\lambda_{n}$$ is the singular value for $$n$$th IPC and correspondingly $$\lambda_{n}^{2}$$ is its eigen value; and $$\gamma_{in}$$ is the eigenvector value for $$i$$th genotype.

### Value

A data frame with the following columns:

 ASTAB The ASTAB values. SSI The computed values of simultaneous selection index for yield and stability. rASTAB The ranks of ASTAB values. rY The ranks of the mean yield of genotypes. means The mean yield of the genotypes.

The names of the genotypes are indicated as the row names of the data frame.

### References

Rao AR, Prabhakaran VT (2005). “Use of AMMI in simultaneous selection of genotypes for yield and stability.” Journal of the Indian Society of Agricultural Statistics, 59, 76–82.

AMMI, SSI

### Examples

library(agricolae)
data(plrv)

# AMMI model
model <- with(plrv, AMMI(Locality, Genotype, Rep, Yield, console = FALSE))

# ANOVA
model$ANOVA # IPC F test model$analysis

# Mean yield and IPC scores
model$biplot # G*E matrix (deviations from mean) array(model$genXenv, dim(model$genXenv), dimnames(model$genXenv))

# With default n (N') and default ssi.method (farshadfar)
ASTAB.AMMI(model)

# With n = 4 and default ssi.method (farshadfar)
ASTAB.AMMI(model, n = 4)

# With default n (N') and ssi.method = "rao"
ASTAB.AMMI(model, ssi.method = "rao")

# Changing the ratio of weights for Rao's SSI
ASTAB.AMMI(model, ssi.method = "rao", a = 0.43)



[Package ammistability version 0.1.2 Index]