[R] dose-response on a grid
Christian Ritz
ritz at kvl.dk
Thu Jul 12 14:23:11 CEST 2007
Hi Bill,
have a look at the following artificial example:
## Loading the package 'drc' (on CRAN)
library(drc)
## Generating dataset with four dose-response curves
finneyx4 <- rbind(finney71, finney71, finney71, finney71)
## Generating artificial points (x,y)
## different pairs for each of the 4 curves in the above dataset
finneyx4$x <- rep(1, 24)
finneyx4$y <- rep(1:4, c(6, 6, 6, 6))
## Fitting the two-parameter log-logistic model (logistic regression)
m1 <- drm(affected/total ~ dose, as.factor(x):as.factor(y), weights = total,
data = finneyx4, fct = LL.2(), type = "binomial")
## Calculating ED50/LD50 for each location (they are all the same for this dataset)
ED(m1, 50)
You could try the same approach for your data!
Christian
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