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
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