Hello dear all, I am trying to adjust a calibration curve for estradiol measurement using ELISA. The suggested method is the 4 parameter Rodbard or the 4 parameters Marquardt. I am trying to use the drc package in R. These functions are not available there I would like to know if anyone can recommend me a function to replace this one or any other ideas to calculate this results. I am attaching a graph of the calibration curve.