doLoewe {mixlow} | R Documentation |
Uses parameter and covariance estimates produced by
doNlme
to estimate Loewe indices and confidence
intervals at different fraction affected values.
doLoewe(mixlowData, nlmeData, verbose)
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 . |
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.
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.
John Boik jcboik@stanford.edu
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
# 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)