  Understanding the nature of glass transition, as well as precise estimation
of the glass transition temperature for polymeric materials, remain open
questions in both experimental and theoretical polymer sciences. We propose a
data-driven approach, which utilizes the high-resolution details accessible
through the molecular dynamics simulation and considers the structural
information of individual chains. It clearly identifies the glass transition
temperature of polymer melts of weakly semiflexible chains. By combining
principal component analysis and clustering, we identify the glass transition
temperature in the asymptotic limit even from relatively short-time
trajectories, which just reach into the Rouse-like monomer displacement regime.
We demonstrate that fluctuations captured by the principal component analysis
reflect the change in a chain's behaviour: from conformational rearrangement
above to small rearrangements below the glass transition temperature. Our
approach is straightforward to apply, and should be applicable to other
polymeric glass-forming liquids.
