Comparison of parameters
Compare parameters from different assays, either by means of ratios or differences.
compParm(object, strVal, operator = "/", vcov. = vcov, od = FALSE, pool = TRUE, display = TRUE)
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. |
vcov. |
function providing the variance-covariance matrix. |
od |
logical. If TRUE adjustment for over-dispersion is used. |
pool |
logical. If TRUE curves are pooled. Otherwise they are not. This argument only works for models with
independently fitted curves as specified in |
display |
logical. If TRUE results are displayed. Otherwise they are not (useful in simulations). |
The function compares actual parameter estimates, and therefore the results depend on the parameterisation used. Probably it is most useful
in combination with the argument collapse in drm for specifying parameter constraints in models, either through
data frames or lists with formulas without intercept (-1).
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).
Christian Ritz
# Fitting a model with names assigned to the parameters!
spinach.m1 <- drm(SLOPE~DOSE, CURVE, data = spinach,
fct = LL.4(names = c("b", "lower", "upper", "ed50")))
## Calculating ratios of parameter estimates for the parameter named "ed50"
compParm(spinach.m1, "ed50")
## Calculating differences between parameter estimates for the parameter named "ed50"
compParm(spinach.m1, "ed50", "-")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.