startEmax: Compute starting parameter values for the 3- or 4- Emax model.

Description

Compute starting parameter values for iterative procedures for estimating parameters of the 3- or 4- parameter Emax model

Usage

startEmax(y,
          dose,
          baseline,
          count=rep(1,length(y)),
          modType=3,
          binary=FALSE,
          lbED50=doselev[2]/10,
          ubED50=max(doselev),
          lbLambda=0.5,
          ubLambda=5)

Value

Returns a vector with named elements for the starting values for a 3 or 4 parameter Emax model. The order is log(ED50), (lambda, 4 parm), emax, and e0. If baseline is specified, a 'beta' starting parameter is also returned at the end of the vector.

Arguments

y: Outcome (response) variable for the Emax modeling.
binary: The default is continuous (binary=FALSE). When (binary=TRUE), y must be 0/1 and starting values are returned for an Emax model on the logit scale.
dose: Dose variable corresponding to each outcome value.
baseline: Optional baseline covariate(s) of same length as y. When baseline is specified, starting values are created from anacova adjusted dose group means.
count: Counts for the number of patients with each dose/y value. Default is 1 (ungrouped data).
modType: modType=3 (default) for the 3-parameter Emax model. modType=4 for the 4-parameter Emax model.
lbED50: If the starting ED50 is below lbED50, it is set to lbED50.
ubED50: If the starting ED50 is above ubED50, it is set to ubED50.
lbLambda: If the starting lambda is below lbLambda, it is set to lbLambda.
ubLambda: If the starting lambda is above ubLambda, it is set to ubLambda.

Author

Neal Thomas

Examples

Run this code

data("metaData")
exdat<-metaData[metaData$taid==6 & metaData$poptype==1,]

startEmax(exdat$rslt,exdat$dose)

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