Sören Vogel <sovo0815 <at> gmail.com> writes: > > Hello, after calculating a multinomial logit regression on my data, I > compared the output to an output retrieved with SPSS 18 (Mac). The > coefficients appear to be the same, but the logLik (and therefore fit) > values differ widely. Why?
Since constants that are independent of the model parameters can be left out of a log-likelihood calculation without affecting inference among models, it is quite common for likelihoods to be calculated differently in different software packages (for example, the (n/2 log(2*pi)) constant in the Gaussian log-likelihood) -- this is true even among different computations within the R ecosystem. What's important is the difference among log-likelihoods between models, which is the same (up to the numeric precision of what you've shown us) for both software packages. > 135.02-129.8 [1] 5.22 > 204.2904-199.0659 [1] 5.2245 Ben Bolker ______________________________________________ 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.
