[R] how to interpolate a plot with a logistic curve

[Christian Ritz]

Dear Simone,

you can use the package 'drc' to fit a logistic model, that is a non-linear regression 
model based on the equation c+(d-c)/(1+exp(b(x-e))), to your data (below named 'simone'):


## Fitting a 4-parameter logistic model (also called Boltzmann model)
simone.m1 <- drm(size~x, data=simone, fct=B.4())

## Plotting the data together with the fitted curve
plot(simone.m1, log="")


The fit is not great due to the bend.


Christian