Can youj please be more specific in your question? What are log files, what are you trying to do, and what kind of answers are you expecting? 

I may be wrong, but I get the feeling that each log file is generated under a specific set of conditions, and so each one is unique and independent (in most ways) of any other log file. Thus, they can't be joined because they are scaled differently.

Dear Dr. Roper, 

           Thank you for your reply. I have four loci sequences, and I run them in starbeast to get a Bayesian Skyline Plot (BSP) . However, after running, I get one log file and four tree files. Just like the picture below. 

          To reconstruct Bayesian Skyline using Tracer, I have to choose one tree file. However, I don't know which tree file should I choose (actually, I want to choose them all). If I have only one locus, it is easy to get a BSP. But I have four loci, and I should not concatenated them since there is a problem of recombination.

        So, if I want to get a BSP using four loci simultaneously, what should I do?

Thanks again for your help!

Best regards,

Sandy

Dea Santiago,

Thank you for your reply. I have found the answer. That is different log files have different column order. I have to sort them if I want to combine them. However, most of the time, they are converging at different likelihoods, as you mentioned.