R: Calculating yield loss parameters

yieldLoss {drc} | R Documentation

## Calculating yield loss parameters

### Description

Calculation of parameters in the re-parameterization of the Michaelis-Menten model that is commonly used to assess yield loss (the rectangular hyperbola model)

### Usage

      yieldLoss(object, interval = c("none", "as"), level = 0.95, display = TRUE)

### Arguments

`object` | object of class 'drc
`interval` | character string specifying the type of confidence intervals to be supplied. The default is "none". Use "as" for asymptotically-based confidence intervals.
`level` | numeric. The level for the confidence intervals. The default is 0.95.
`display` | logical. If TRUE results are displayed. Otherwise they are not (useful in simulations).

### Details

The rectangular hyperbola model is a reparameterization of the Michaelis-Menten in terms of parameters A and I

Y_L = \frac{Id}{1+Id/A}

where d denotes the weed density and Y_L the resulting yield loss.

### Value

For each of the two parameters, a matrix with two or more columns, containing the estimates and the corresponding estimated standard errors and possibly lower and upper confidence limits.

### Note

This function is only for use with model fits based on Michaelis-Menten models.

### Author(s)

Christian Ritz

### References

Cousens, R. (1985). A simple model relating yield loss to weed density, Ann. Appl. Biol., 107, 239–252.

### Examples

    ## Fitting Michaelis-Menten model
    met.mm.m1 <- drm(gain~dose, product, data = methionine, fct = MM.3(),
    pmodels = list(~1, ~factor(product), ~factor(product)))

    ## Yield loss parameters with standard errrors
    yieldLoss(met.mm.m1)

    ## Also showing confidence intervals
    yieldLoss(met.mm.m1, "as")

[Package drc version 3.0-1 Index]