stability.tai: Tai's stability analysis

In agrostab: Stability Analysis for Agricultural Research

Description

This function calculates the Tai's stability parameters.

Usage

stability.tai(dataf, res_var, gen_var, env_var, rep_var, plotIt = TRUE)

Arguments

dataf	the name of the data frame containing the data to analyze.
res_var	the response variable.
gen_var	the genotypes variable.
env_var	the environments variable.
rep_var	the replications variable.
plotIt	a logical value specifying if plot should be drawn; default is TRUE

Value

Returns a list of two objects:

ANOVA

the analysis of variance table

scores

the data frame object of stability analysis results:

• alpha regression of genotype means on environmental means

• t_value t-values for gypothesis that alpha=0

• p_value p-values for gypothesis that alpha=0

• lambda deviation from linear responses

• pf_value p-values for gypothesis that lambda=0

References

Tai, G.C.C. 1971. Genotypic stability analysis and application to potato regional trials. Crop Sci. 11: 184-190. doi:10.2135/cropsci1971.0011183X001100020006x

Examples

data(exp_data)
stability.tai(exp_data,"yield","gen","env","rep")

Example output

$ANOVA
                     Df Sum Sq Mean Sq  F value    Pr(>F)    
Environments          5 89.302 17.8604 542.4771 1.065e-13 ***
Rep. in Env.         12  0.395  0.0329   3.3632 0.0006386 ***
Genotypes             6 13.505  2.2508   7.3527 6.727e-05 ***
Gen. x Env.          30  9.184  0.3061  31.2702 < 2.2e-16 ***
  Linear responses    6  2.142  0.3569   1.2164 0.3322784    
  Dev. from lin.res. 24  7.042  0.2934  29.9730 < 2.2e-16 ***
Error                72  0.705  0.0098                       
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

$scores
                alpha   t_value    p_value    lambda     pf_value
Novosib2   0.10457692 0.4284848 0.69036385 72.177000 1.110223e-16
Novosib3   0.02338189 0.1538333 0.88519031 27.995530 1.302143e-10
Novosib32 -0.35015136 2.9170499 0.04337118 17.391987 5.002283e-08
Novosib40  0.13641109 2.0539155 0.10920381  5.334851 1.768947e-03
Novosib51 -0.05343879 0.8662612 0.43521588  4.609990 4.149523e-03
Obskaya_o  0.03341378 0.2790395 0.79404724 17.375575 5.057109e-08
Omskaya6   0.10580648 0.7669413 0.48587883 23.057760 1.636956e-09

agrostab documentation built on Oct. 30, 2019, 10:51 a.m.