I have insect size measurements that I fit to a Weibull curve
to determine EC50. ?This is my model
fit:model=nls(y~SSweibull(x,asym,drop,lrc,pwr))
I need to use the untreated buffer samples as the maximum size
(the left most asymptope). ?If I put the doses
as 0,1,2,4,8,16,32,64,128 ppm,
I get error messages indicating that 0 values for x are inappropriate.
?This is the error message:Error in qr.default(.swts *
attr(rhs, "gradient")) :?? NA/NaN/Inf in
foreign function call (arg 1)?
I found that I get more consistent results when I put
0.01 for the dose of the untreated controls. ?I was
wondering if there was a convention to follow when using
untreated buffer samples in EC50 calculations. ?Cheers,Katie