> orl.nl1 <- nls(ffe ~ b0 + ((b1*orl_dose)/(b2+orl_dose)), + start=c(b0=1, b1=1, b2=1)) > > summary(orl.nl1) Formula: ffe ~ b0 + ((b1 * orl_dose)/(b2 + orl_dose)) Parameters: Estimate Std. Error t value Pr(>|t|) b0 6.115 1.077 5.679 6.22e-08 *** b1 27.625 3.476 7.948 3.21e-13 *** b2 124.732 47.788 2.610 0.00991 ** --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 8.994 on 160 degrees of freedom Number of iterations to convergence: 13 Achieved convergence tolerance: 7.296e-06 > vcov(orl.nl1) b0 b1 b2 b0 1.1594479 -0.7218709 15.60886 b1 -0.7218709 12.0809731 130.13601 b2 15.6088629 130.1360073 2283.72973 >