Lemna

Data from a dose-response experiment with the aquatic plant Lemna minor (duckweed). The response measured was the frond number (count) at different concentrations of a test substance.

Usage

data(lemna)

Format

A data frame with 44 observations on the following 2 variables.

conc

a numeric vector containing the concentration.

frond.num

a numeric vector containing the response (count).

Examples

library(drc)

## Displaying the data
head(lemna)
#>   conc frond.num
#> 1    0        70
#> 2    0        66
#> 3    0        61
#> 4    0        65
#> 5    0        65
#> 6    0        61

## Fitting a four-parameter log-logistic model
lemna.m1 <- drm(frond.num ~ conc, data = lemna, fct = LL.4())
summary(lemna.m1)
#> 
#> Model fitted: Log-logistic (ED50 as parameter) (4 parms)
#> 
#> Parameter estimates:
#> 
#>               Estimate Std. Error t-value   p-value    
#> b:(Intercept)  0.80378    0.13342  6.0246 4.364e-07 ***
#> c:(Intercept) 25.12544    4.10027  6.1278 3.125e-07 ***
#> d:(Intercept) 65.67420    1.09101 60.1957 < 2.2e-16 ***
#> e:(Intercept) 10.05380    3.20991  3.1321  0.003241 ** 
#> ---
#> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#> 
#> Residual standard error:
#> 
#>  3.240232 (40 degrees of freedom)

## Plotting the fitted curve
plot(lemna.m1, xlab = "Concentration", ylab = "Frond number")