r - strain pH response curve

Question

I have measured growth rates in different pH levels and I want to fit the data with a curve to get the growth ranges of my strains (minimal pH - optimal pH - maximal pH)

I tried 3rd order polynomial to allow the curve to be asymmetric, but in some cases the function does not have two solutions for y=0 and therefore I am not able to compute one of the extremes.

Can you suggest another function (ideally biologically meaningful) to fit my data or some way to force 3rd polynomial to do the work.

My data in R look as follows (x - pH; y - growth rate):

x <- c(3, 3.5, 4, 4.5, 5, 6, 7)

y <- c(0.217, 0.303, 0.326, 0.353, 0.416, 0.501, 0.275)

question from:https://stackoverflow.com/questions/65892239/strain-ph-response-curve

Answer 1

Waitting for answers