Small plants of Galium aparine, growing in pots in a green house, were sprayed with the technical grade phenmidipham herbicide either alone or in mixture with an ester of oleic acid. The plants were allowed to grow in the green house for 14 days after herbicide treatment. Then the dry matter was measured per pot.
A data frame with 240 observations on the following 3 variables.
a numeric vector of dose value (g/ha)
a numeric vector of dry matter weights (mg/pot)
a numeric vector giving the grouping: 0: control, 1,2: herbicide formulations
Cabanne, F., Gaudry, J. C. and Streibig, J. C. (1999) Influence of alkyl oleates on efficacy of phenmedipham applied as an acetone:water solution on Galium aparine, Weed Research, 39, 57–67.
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## Fitting a model with a common control (so a single upper limit: "1") G.aparine.m1 <- drm(drymatter ~ dose, treatment, data = G.aparine, pmodels = data.frame(treatment, treatment, 1, treatment), fct = LL.4()) ## Visual inspection of fit plot(G.aparine.m1, broken = TRUE) ## Lack of fit test modelFit(G.aparine.m1) ## Summary output summary(G.aparine.m1) ## Predicted values with se and confidence intervals #predict(G.aparine.m1, interval = "confidence") # long output ## Calculating the relative potency EDcomp(G.aparine.m1, c(50,50)) ## Showing the relative potency as a ## function of the response level relpot(G.aparine.m1) relpot(G.aparine.m1, interval = "delta") # appears constant! ## Response level in percent relpot(G.aparine.m1, scale = "percent") ## Fitting a reduced model (with a common slope parameter) G.aparine.m2 <- drm(drymatter ~ dose, treatment, data = G.aparine, pmodels = data.frame(1, treatment, 1, treatment), fct = LL.4()) anova(G.aparine.m2, G.aparine.m1) ## Showing the relative potency relpot(G.aparine.m2) ## Fitting the same model in a different parameterisation G.aparine.m3 <- drm(drymatter ~ dose, treatment, data = G.aparine, pmodels = data.frame(treatment, treatment, 1, treatment), fct = LL2.4()) EDcomp(G.aparine.m3, c(50, 50), logBase = exp(1))
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