# R/SSpoly2.R In OnofriAndreaPG/aomisc: Statistical methods for the agricultural sciences

#### Documented in poly2.fun

```#Polynomial regression (2nd order) ##############################################
poly2.fun <- function(predictor, a, b, c) {
a + b * predictor + c * (predictor^2)
}

poly2.Init <- function(mCall, LHS, data, ...) {
xy <- sortedXyData(mCall[["predictor"]], LHS, data)
lmFit <- lm((xy[, "y"]) ~ xy[, "x"] + I( xy[, "x"]^2))
coefs <- coef(lmFit)
a <- coefs[1]
b <- coefs[2]
c <- coefs[3]
value <- c(a, b, c)
names(value) <- mCall[c("a", "b", "c")]
value
}
NLS.poly2 <- selfStart(poly2.fun, poly2.Init, parameters=c("a", "b", "c"))

"DRC.poly2" <- function(fixed = c(NA, NA, NA), names = c("a", "b", "c"))
{
## Checking arguments
numParm <- 3
if (!is.character(names) | !(length(names) == numParm)) {stop("Not correct 'names' argument")}
if (!(length(fixed) == numParm)) {stop("Not correct 'fixed' argument")}

## Fixing parameters (using argument 'fixed')
notFixed <- is.na(fixed)
parmVec <- rep(0, numParm)
parmVec[!notFixed] <- fixed[!notFixed]

## Defining the non-linear function
fct <- function(x, parm)
{
parmMat <- matrix(parmVec, nrow(parm), numParm, byrow = TRUE)
parmMat[, notFixed] <- parm

a <- parmMat[, 1]; b <- parmMat[, 2]; c <- parmMat[, 3]
a + b * x + c * (x^2)
}

## Defining self starter function
ssfct <- function(dataf)
{
x <- dataf[, 1]
y <- dataf[, 2]

#regression on pseudo y values
pseudoY <- y
pseudoX <- x
coefs <- coef( lm(pseudoY ~ pseudoX + I(pseudoX^2)) )
a <- coefs[1]
b <- coefs[2]
c <- coefs[3]

return(c(a, b, c)[notFixed])
}

## Defining names
pnames <- names[notFixed]

## Defining derivatives
deriv1 <- function(x, parm){
d1 <- rep(1, length(x) )
d2 <- x
d3 <- x^2
cbind(d1, d2, d3)
}
## Defining the ED function

## Defining the inverse function

## Defining descriptive text
text <- "Second Order Polynomial"

## Returning the function with self starter and names
returnList <- list(fct = fct, ssfct = ssfct, names = pnames,
text = text, noParm = sum(is.na(fixed)), deriv1 = deriv1)

class(returnList) <- "drcMean"
invisible(returnList)
}
```
OnofriAndreaPG/aomisc documentation built on Feb. 26, 2024, 8:21 p.m.