drc (version 1.2-0)

compParm: Comparison of parameters

Description

Compare parameters from different assays, either by means of ratios or differences.

Usage

compParm(object, strVal, operator = "/", od = FALSE)

Arguments

object

an object of class 'drc'.

strVal

a name of parameter to compare.

operator

a character. If equal to "/" (default) parameter ratios are compared. If equal to "-" parameter differences are compared.

od

logical. If TRUE adjustment for over-dispersion is used.

Value

• A matrix with columns containing the estimates, estimated standard errors, values of t-statistics and p-values for the null hypothesis that the ratio equals 1 or that the difference equals 0 (depending on the operator argument). No adjustment for multiplicity is applied. See p.adjust on how to do adjust p-values.

Details

The function compares actual parameter estimates, and therefore the results depend on the parameterisation used. Probably it is most useful in combination with 'collapse' arguments (in multdrc) that are data frames or lists with formulas without intercept (-1).

Examples

# Fitting a model with names assigned to the parameters!
model1 <- multdrc(SLOPE~DOSE, CURVE, data=PestSci,
fct=l4(names = c("b", "lower", "upper", "ed50")))

## Calculating ratios of parameter estimates for the parameter named "ed50"
compParm(model1, "ed50")      

## Calculating differences between parameter estimates for the parameter named "ed50"
compParm(model1, "ed50", "-")  

rm(model1)