Commit 7c35ffe7 authored by Vallo Varik's avatar Vallo Varik
Browse files

Work on text

parent 34067265
......@@ -32,7 +32,7 @@ str(ryegrass)
?ryegrass
```
The workhorse of the `drc` is function `drm` (Dose-Response Model) and it works pretty similarly to `lm` which we used to fit linear model. The only new thing is `fct` argument. `fct` defines the exact function to be used and some sane initial values for parameters. For four parameter logistic regression, we need to set `fct = LL.4` (log-logistic with 4 parameters, the extra "log" is just to denote that x-axis is in log scale; there is also LL.3 for instance, this sets slope to be 1).
The workhorse of the `drc` is function `drm` (Dose-Response Model) and it works pretty similarly to `lm` which we used to fit linear model. The only new thing is `fct` argument. `fct` defines the exact function to be used and some sane initial values for parameters (contrary to linear regression, estimation of parameters in non-linear regression requires some starting estimates of parameter values). For four parameter logistic regression, we need to set `fct = LL.4` (log-logistic with 4 parameters, the extra "log" is just to denote that x-axis is in log scale; e.g. there is also LL.3, three parameter version, this sets slope to be 1).
```{r}
mod = drm(rootl ~ conc, data = ryegrass, fct = LL.4())
......
......@@ -26,10 +26,13 @@ vector of concentrations of a herbicide.
The workhorse of the `drc` is function `drm` (Dose-Response Model) and
it works pretty similarly to `lm` which we used to fit linear model. The
only new thing is `fct` argument. `fct` defines the exact function to be
used and some sane initial values for parameters. For four parameter
used and some sane initial values for parameters (contrary to linear
regression, estimation of parameters in non-linear regression requires
some starting estimates of parameter values). For four parameter
logistic regression, we need to set `fct = LL.4` (log-logistic with 4
parameters, the extra “log” is just to denote that x-axis is in log
scale; there is also LL.3 for instance, this sets slope to be 1).
scale; e.g. there is also LL.3, three parameter version, this sets slope
to be 1).
mod = drm(rootl ~ conc, data = ryegrass, fct = LL.4())
......
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