I'm using the tidydrc package (a tidy wrapper for drc) for doing a standardized dose-response curve.
There is an option to draw the line at 50, but it is usually not correct. See screenshot below (green arrow is true 50).
I have minimal reprex code below, so I'm wondering.....in the result (my result) can you help me find if the actual coordinates for the fit line are within? Don't some curve-fitting models actually return the coordinates (something like 0.01 intervals)? I can't seem to find it, but if that's retrievable I could just find the value that's closest to 50.
library(tidydrc) mydf <- data.frame("dose"=c(1900,950,475,237.5,118.75,59.375,29.68,14.843,7.421,3.71), "response"=c(100.23,96.41,93.56,91.87,55.41,45.503,36.86,27.16,18.80,12.65)) myresult <- tidydrc_model(mydf, dose=dose, response=response, model=LL.4()) tidydrc_plot(myresult,ed50 = TRUE)