On 8/07/10 14:52 PM, "Manuel Spínola" <mspinol...@gmail.com> wrote:
> Dear list members, > > I am using function invlogit from the "arm" package to get the > difference in probabilities for a explanatory factor from the model > below (I am working with factor "iluminacion"). > Manuel, You do not need any special packages (like "arm") to handle logits, since basic R has function plogis() for the job. >> invlogit(-0.4241 - 0.4804 * 0) - invlogit(-0.4241 - 0.4804 * 1) # > difference in probability for iluminacion > [1] 0.1074094 > > How can I transform the standard error of the difference from logit to > probability? > Make calculations in the scale of the linear predictor and then use plogis() to change the result to the scale of response (probability). With usual assumption. Cheers, Jari Oksanen > The standard error in logits is 0.2416 (taken from the model below). > > Best, > > Manuel > > >> summary(mod6) > > Call: > glm(formula = condicion ~ iluminacion + animales + cielo.raso + > piso + paredes, family = binomial, data = reglog) > > Deviance Residuals: > Min 1Q Median 3Q Max > -1.2527 -1.0034 -0.8276 1.2208 1.6981 > > Coefficients: > Estimate Std. Error z value Pr(>|z|) > (Intercept) -0.4241 0.2833 -1.497 0.1343 > iluminacion[T.1] -0.4804 0.2416 -1.988 0.0468 * > animales[T.1] 0.4613 0.2385 1.934 0.0531 . > cielo.raso[T.1] -0.1386 0.2840 -0.488 0.6254 > piso[T.1] 0.1380 0.2934 0.470 0.6382 > paredes[T.1] -0.1289 0.3012 -0.428 0.6687 > --- > Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > > (Dispersion parameter for binomial family taken to be 1) > > Null deviance: 433.04 on 319 degrees of freedom > Residual deviance: 424.30 on 314 degrees of freedom > (25 observations deleted due to missingness) > AIC: 436.3 > > Number of Fisher Scoring iterations: 4 > _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
