index.smith: Uniformity soil. Smith's Index of Soil Heterogeneity

In agricolae: Statistical Procedures for Agricultural Research

Uniformity soil. Smith's Index of Soil Heterogeneity

Description

Smith's index of soil heterogeneity is used primarily to derive optimum plot size. The index gives a single value as a quantitative measure of soil heterogeneity in an area. Graph CV for plot size and shape.

Usage

index.smith(data, PLOT=TRUE,...)

Arguments

data	dataframe or matrix
PLOT	graphics, TRUE or FALSE
...	Parameters of the plot()

Details

Vx=V(x)/x b

V(x) is the between-plot variance, Vx is the variance per unit area for plot size of x basic unit, and b is the Smith' index of soil heterogeneity.

Value

model	function pattern of uniformity
uniformity	Table of the soil uniformity

Author(s)

Felipe de Mendiburu

References

Statistical Procedures for Agriculture Research. Second Edition. Kwanchai A. Gomez and Arturo A. Gomez. 1976. USA

Examples

library(agricolae)
data(rice)
#startgraph
table<-index.smith(rice,
 main="Relationship between CV per unit area and plot size",col="red")
#endgraph
uniformity <- data.frame(table$uniformity)
uniformity
# regression variance per unit area an plot size.
model <- lm(Vx ~ I(log(Size)),uniformity)
coeff <- coef(model)
x<-1:max(uniformity$Size)
Vx<- coeff[1]+coeff[2]*log(x)
#startgraph
plot(x,Vx, type="l", col="blue",
 main="Relationship between variance per unit area and plot size")
points(uniformity$Size,uniformity$Vx)
#endgraph

agricolae documentation built on Oct. 23, 2023, 1:06 a.m.