Logarithmic frequency in morphic sequences (Q1011951)

This paper answers a question raised by [\textit{J.-P. Allouche} and \textit{J. Shallit}, Automatic sequences. Theory, applications, generalizations. Cambridge: Cambridge University Press (2003; Zbl 1086.11015)] by showing that the logarithmic frequency of letters appearing in a morphic sequence always exists. This extends a result of \textit{A. Cobham} [Math. Syst. Theory 6, 164--192 (1972; Zbl 0253.02029)] showing that the logarithmic frequency of letters appearing in an automatic sequence always exists, while the natural frequency need not exist.