drfit {drfit} | R Documentation |
Fit dose-response relationships to dose-response data and calculate biometric results for (eco)toxicity evaluation
drfit(data, startlogED50 = NA, chooseone = TRUE, probit = TRUE, logit = FALSE, weibull = FALSE, linlogit = FALSE, conf = FALSE, linlogitWrong = NA, allWrong = NA, s0 = 0.5, b0 = 2, f0 = 0)
data |
A data frame containing dose-response data. The data frame has to contain
at least a factor called “substance”, a numeric vector “dose”
with the dose values, a vector called “unit” containing the unit
used for the dose and a numeric vector “response” with the response
values of the test system normalized between 0 and 1. Such a data frame can
be easily obtained if a compliant RODBC data source is available for use in
conjunction with the function drdata .
If there is a column called “ok” and it is set to “no fit” in a specific line, then the corresponding data point will be excluded from the fitting procedure, although it will be plotted. |
startlogED50 |
Especially for the linlogit model, a suitable log10 of the ED50 has to be given by the user, since it is not correctly estimated for data showing hormesis with the default estimation method. |
probit |
A boolean defining if cumulative density curves of normal distributions
pnorm are fitted against the decadic logarithm of the dose.
Default ist TRUE. |
logit |
A boolean defining if cumulative density curves of logistic distributions
plogis are fitted to the decadic logarithm of the dose.
Default is FALSE. |
weibull |
A boolean defining if the cumulative density curves of weibull distributions
(pweibull with additionall location parameter and scale=1)
are fitted to the decadic logarithm of the dose. Default is FALSE. |
linlogit |
A boolean defining if the linear-logistic function
linlogitf as defined by van Ewijk and Hoekstra 1993 is
fitted to the data. Default is FALSE. |
conf |
A boolean defining if a confidence interval of the log ED50 is to be listed for alpha = 5 % (two-sided). If FALSE (default), the standard deviation is listed in the output of drfit. |
linlogitWrong |
An optional vector containing the names of the substances for which the linlogit function produces a wrong fit. |
allWrong |
An optional vector containing the names of the substances for which all functions produce a wrong fit. |
chooseone |
If TRUE (default), the models are tried in the order linlogit, probit, logit, weibull, and the first model that produces a valid fit is used. If FALSE, all models that are set to TRUE and that can be fitted will be reported. |
s0 |
If the weibull model is fitted, s0 gives the possibility to adjust the
starting value for the shape parameter of pweibull . |
b0,f0 |
If the linearlogistic model is fitted, b0 and f0 give the possibility to adjust the starting values for the parameters b and f. |
results |
A data frame containing at least one line for each substance. If the data
did not show a mean response < 0.5 at the highest dose level, the
modeltype is set to “inactive”. If the mean response at the lowest
dose is smaller than 0.5, the modeltype is set to “active”. In
both cases, no fitting procedure is carried out. Every successful fit is
reported in one line. Parameters of the fitted curves are only reported
if the fitted ED50 is not higher than the highest dose.
ndl is the number of dose levels in the raw data, n is the
total number of data points in the raw data used for the fit
lld is the decadic logarithm of the lowest dose and
lhd is the decadic logarithm of the highest dose. For the
“linlogit”, “logit” and “probit” models, the
parameter a that is reported coincides with the logED50, i.e the
logED50 is one of the model parameters that is being fitted, and
therefore, depending on the argument conf , a standard deviation
std or a confidence interval conf is reported for the
logED50. In the case of the “weibull” model, a is a
location parameter. Parameter b in the case of the
“linlogit” fit is the variable b from the linlogitf
function. In the case of “probit” fit it is the standard deviation
of the fitted normal distribution, in the case of the “logit” fit
it is the scale parameter in the plogis function,
and in the “weibull” fit it is the shape parameter of the
fitted pweibull function. Only the “linlogit” fit
produces a third parameter c which is the variable f from the
linlogitf function. |
Johannes Ranke jranke@uni-bremen.de http://www.uft.uni-bremen.de/chemie/ranke
data(antifoul) r <- drfit(antifoul) format(r,digits=2)