> spwt.fmod <- nls(weight ~ b0+(b1*temp)+(b3*(b2^dilute)), start=c(b0=1, b1=-1, b2=-1, b3=1)) > > summary(spwt.fmod) Formula: weight ~ b0 + (b1 * temp) + (b3 * (b2^dilute)) Parameters: Estimate Std. Error t value Pr(>|t|) b0 2.9125e+03 1.1481e+00 2536.92 < 2.2e-16 *** b1 -1.2869e+00 4.9550e-03 -259.71 < 2.2e-16 *** b2 9.8416e-01 9.0519e-05 10872.39 < 2.2e-16 *** b3 -3.8599e+02 9.5977e-01 -402.16 < 2.2e-16 *** --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 1.8998 on 311 degrees of freedom Number of iterations to convergence: 17 Achieved convergence tolerance: 5.1439e-07 >