yieldLoss function

Calculating yield loss parameters

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

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 $I$

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

Returns

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.

References

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

Author(s)

Christian Ritz

Note

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

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")