doLoewe {mixlow}R Documentation

Estimate Loewe indices and confidence intervals

Description

Uses parameter and covariance estimates produced by doNlme to estimate Loewe indices and confidence intervals at different fraction affected values.

Usage

doLoewe(mixlowData, nlmeData, verbose)

Arguments

mixlowData A list obtained from the output of prepareData
nlmeData A list obtained from the output of doNlme
verbose An optional logical value. If TRUE, information from intermediate steps in the Loewe analysis is printed. Default is FALSE.

Details

Loewe indices are estimated based on parameter and covariance values generated by use of the doNlme function. In addition to returning interaction indices, the doLoewe function returns a vector indicating the degree of statistically significant synergism at each fraction affected value. The degree of statistically significant synergism at each fraction affected value is zero if the upper confidence limit is above 1.0, and is the difference between the upper confidence limit and 1.0 otherwise. A vector of statistically significant antagonism is calculated in an analogous manner. These vectors summarize the degree of synergism/antagonism occurring over a range of fraction affected values.

The width of the index confidence intervals is dependent in part on the critical value taken from the t-distribution, which in turn is dependent on the degrees of freedom. For multiple drug analysis with doNlme, the degrees of freedom is taken directly from the nlme results. For single drug analysis, the degrees of freedom is taken as the minimum degrees of freedom over all drugs.

Value

A list with the following named components:

drugs The drugs analyzed
mix The mixture analyzed
ciL A data frame containing Loewe index estimates and confidence intervals based on the log of the index, for different fraction affected values
covv Covariance matrix of the parameter estimates
g0 gamma, shape parameters
p0 psi, IC50 parameters
uu u parameter
dat0 Data frame containing concentration-response values
score.interval Interval of fraction affected values over which synergism/antagonism scores were computed
syner Synergism scores for fraction affected values in interval
syner.total Sum of synergism scores over interval
antag Antagonism scores for fraction affected values in interval
antag.total Sum of antagonism scores over interval


See doNlme for a description of gamma, psi, and u parameters.

Author(s)

John Boik jcboik@stanford.edu

References

The model is described in Boik J.C., Newman R.A., Boik R.J. (2008) Quantifying synergism/antagonism using nonlinear mixed-effects modeling: a simulation study. Statistics in Medicine 27(7), 1040-61

See Also

doNlme, plotLoeweData

Examples

# mixlowData data object is obtained using the prepareData function
data(mixlowData)
# nlmeData data object is obtained using the doNlme function
data(nlmeData)
loeweData <- doLoewe(mixlowData, nlmeData)

[Package mixlow version 0.01.1 Index]