Hi, I am using the following dataset and fitting a 4 parameter logistical curve using drm. However, there is no p value returned for any of the fitted coefficients and a warning message of NaNs produced is returned. I tried using both LL.4 and LL2.4. What does the warning message imply? The data fitted here does not quite match up with the results of Masterplex software. What may I be doing wrong? Please help.
Weights <-1/(y1^2) list(all) [[1]] x1 y1 1 1500.00 439908 2 1500.00 464838 3 1500.00 467593 4 150.00 26126 5 150.00 26639 6 150.00 26524 7 25.00 3482 8 25.00 3555 9 25.00 3438 10 5.00 790 11 5.00 826 12 5.00 805 13 2.00 443 14 2.00 464 15 2.00 469 16 1.00 337 17 1.00 355 18 1.00 364 19 0.50 278 20 0.50 279 21 0.50 307 22 0.25 241 23 0.25 266 24 0.25 276 FourPL.fit <- drm(y1~x1,weights=weights,data=all,fct=LL2.4()) summary(FourPL.fit <- drm(y1~x1,weights=weights,data=all,fct=LL2.4())) Model fitted: Log-logistic (log(ED50) as parameter) (4 parms) Parameter estimates: Estimate Std. Error t-value p-value b:(Intercept) -1.144871 0.068434 -16.729579 0 c:(Intercept) 241.482714 7.112223 33.953199 0 d:(Intercept) 423431.818035 NA NA NA e:(Intercept) 7.319215 NA NA NA Residual standard error: 0.0001265872 (20 degrees of freedom) Warning message: In sqrt(diag(varMat)) : NaNs produced > summary(FourPL.fit.1 <- drm(y1~x1,weights=weights,data=all,fct=LL.4())) Model fitted: Log-logistic (ED50 as parameter) (4 parms) Parameter estimates: Estimate Std. Error t-value p-value b:(Intercept) -1.20654 0.07606 -15.86309 0.0000 c:(Intercept) -226.35200 128.30261 -1.76420 0.0930 d:(Intercept) 468060.34801 NA NA NA e:(Intercept) 292.10119 132.92109 2.19755 0.0399 Residual standard error: 0.003207409 (20 degrees of freedom) Warning message: In sqrt(diag(varMat)) : NaNs produced Master Plex summary: Initial Top 462020.7967 Initial Bottom 234.9 Initial MidPoint 784.0181741 Initial HillSlope 1 Weighting 1/y^2 Max Iteration 500 Thanks, Abhi [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.